Containers: suppress literal operator warnings on GCC 15 with -std=c++23.

Same thing as with Clang 17+ (see the comment for why), but in this case
the warning seems to be enabled by default, which is rather annoying.

src/Magnum/Math/Angle.h

@@ -164,10 +164,11 @@ namespace Literals {
    load-bearing in any other contexts. Clang 17+ adds an off-by-default warning
    for this; GCC 4.8 however *requires* the space there, so until GCC 4.8
    support is dropped, we suppress this warning instead of removing the
-   space. */
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-literal-operator"
+   space. GCC 15 now has the same warning but it's enabled by default on
+   -std=c++23. */
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-literal-operator"
 #endif
 /** @relatesalso Magnum::Math::Deg
 @brief Double-precision degree value literal
@@ -192,8 +193,8 @@ Example usage:
 @m_keywords{_degf degf}
 */
 constexpr Deg<Float> operator"" _degf(long double value) { return Deg<Float>(Float(value)); }
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic pop
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic pop
 #endif
 
 }}
@@ -267,10 +268,11 @@ namespace Literals {
    load-bearing in any other contexts. Clang 17+ adds an off-by-default warning
    for this; GCC 4.8 however *requires* the space there, so until GCC 4.8
    support is dropped, we suppress this warning instead of removing the
-   space. */
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-literal-operator"
+   space. GCC 15 now has the same warning but it's enabled by default on
+   -std=c++23. */
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-literal-operator"
 #endif
 /** @relatesalso Magnum::Math::Rad
 @brief Double-precision radian value literal
@@ -289,8 +291,8 @@ See @link operator""_degf() @endlink for more information.
 @m_keywords{_radf radf}
 */
 constexpr Rad<Float> operator"" _radf(long double value) { return Rad<Float>(Float(value)); }
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic pop
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic pop
 #endif
 
 }}

src/Magnum/Math/Color.h

@@ -1502,10 +1502,11 @@ namespace Literals {
    load-bearing in any other contexts. Clang 17+ adds an off-by-default warning
    for this; GCC 4.8 however *requires* the space there, so until GCC 4.8
    support is dropped, we suppress this warning instead of removing the
-   space. */
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-literal-operator"
+   space. GCC 15 now has the same warning but it's enabled by default on
+   -std=c++23. */
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-literal-operator"
 #endif
 /** @relatesalso Magnum::Math::Color3
 @brief 8bit-per-channel linear RGB literal
@@ -1867,8 +1868,8 @@ operator"" _srgbah() {
     return Color4<Half>{Color4<Float>::fromSrgbAlpha(Implementation::color4Literal<Vector4<UnsignedByte>, 1, sizeof...(chars), chars...>())};
 }
 #endif
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic pop
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic pop
 #endif
 
 }}

src/Magnum/Math/Half.h

@@ -192,10 +192,11 @@ namespace Literals {
    load-bearing in any other contexts. Clang 17+ adds an off-by-default warning
    for this; GCC 4.8 however *requires* the space there, so until GCC 4.8
    support is dropped, we suppress this warning instead of removing the
-   space. */
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-literal-operator"
+   space. GCC 15 now has the same warning but it's enabled by default on
+   -std=c++23. */
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-literal-operator"
 #endif
 /** @relatesalso Magnum::Math::Half
 @brief Half-float literal
@@ -203,8 +204,8 @@ namespace Literals {
 See @ref Half for more information.
 */
 inline Half operator"" _h(long double value) { return Half(Float(value)); }
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic pop
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic pop
 #endif
 
 }}

src/Magnum/Math/Time.h

@@ -297,10 +297,11 @@ namespace Literals {
    load-bearing in any other contexts. Clang 17+ adds an off-by-default warning
    for this; GCC 4.8 however *requires* the space there, so until GCC 4.8
    support is dropped, we suppress this warning instead of removing the
-   space. */
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-literal-operator"
+   space. GCC 15 now has the same warning but it's enabled by default on
+   -std=c++23. */
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-literal-operator"
 #endif
 /** @relatesalso Magnum::Math::Nanoseconds
 @brief Nanosecond value literal
@@ -388,8 +389,8 @@ precision on a range of roughly ±2 hours. For example:
 constexpr Nanoseconds<Long> operator"" _sec(long double value) {
     return Nanoseconds<Long>{Long(value*1000000000.0l)};
 }
-#if defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17
-#pragma clang diagnostic pop
+#if (defined(CORRADE_TARGET_CLANG) && __clang_major__ >= 17) || (defined(CORRADE_TARGET_GCC) && !defined(CORRADE_TARGET_CLANG) && __GNUC__ >= 15)
+#pragma GCC diagnostic pop
 #endif
 
 }}