GL: new "intel-windows-broken-dsa-framebuffer-clear" workaround.

I'm too lazy to write the commit messages now.

doc/changelog.dox

@@ -87,6 +87,8 @@ See also:
     -   @cpp "intel-windows-broken-dsa-layered-cubemap-array-framebuffer-attachment" @ce
         fixing @ref GL::Framebuffer::attachLayeredTexture() with
         @ref GL::CubeMapTextureArray
+    -   @cpp "intel-windows-broken-dsa-framebuffer-clear" @ce
+        fixing @ref GL::Framebuffer::clearColor()
 -   New `--magnum-gpu-validation` @ref GL-Context-command-line "command-line option"
     and a corresponding environment variable to conveniently enable
     @gl_extension{KHR,debug} debug output

src/Magnum/GL/Implementation/FramebufferState.cpp

@@ -65,11 +65,6 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
 
         checkStatusImplementation = &AbstractFramebuffer::checkStatusImplementationDSA;
 
-        clearIImplementation = &AbstractFramebuffer::clearImplementationDSA;
-        clearUIImplementation = &AbstractFramebuffer::clearImplementationDSA;
-        clearFImplementation = &AbstractFramebuffer::clearImplementationDSA;
-        clearFIImplementation = &AbstractFramebuffer::clearImplementationDSA;
-
         drawBuffersImplementation = &AbstractFramebuffer::drawBuffersImplementationDSA;
         drawBufferImplementation = &AbstractFramebuffer::drawBufferImplementationDSA;
         readBufferImplementation = &AbstractFramebuffer::readBufferImplementationDSA;
@@ -94,13 +89,6 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
     {
         checkStatusImplementation = &AbstractFramebuffer::checkStatusImplementationDefault;
 
-        #ifndef MAGNUM_TARGET_GLES2
-        clearIImplementation = &AbstractFramebuffer::clearImplementationDefault;
-        clearUIImplementation = &AbstractFramebuffer::clearImplementationDefault;
-        clearFImplementation = &AbstractFramebuffer::clearImplementationDefault;
-        clearFIImplementation = &AbstractFramebuffer::clearImplementationDefault;
-        #endif
-
         #ifndef MAGNUM_TARGET_GLES2
         drawBuffersImplementation = &AbstractFramebuffer::drawBuffersImplementationDefault;
         #endif
@@ -175,6 +163,32 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
     }
     #endif
 
+    /* DSA/non-DSA implementation for framebuffer clearing. Yes, it's because
+       Intel Windows drivers are shit. */
+    #ifndef MAGNUM_TARGET_GLES
+    if(context.isExtensionSupported<Extensions::ARB::direct_state_access>()
+        #ifdef CORRADE_TARGET_WINDOWS
+        && (!(context.detectedDriver() & Context::DetectedDriver::IntelWindows) ||
+            context.isDriverWorkaroundDisabled("intel-windows-broken-dsa-framebuffer-clear"))
+        #endif
+    ) {
+        /* Extension name added above */
+
+        clearIImplementation = &AbstractFramebuffer::clearImplementationDSA;
+        clearUIImplementation = &AbstractFramebuffer::clearImplementationDSA;
+        clearFImplementation = &AbstractFramebuffer::clearImplementationDSA;
+        clearFIImplementation = &AbstractFramebuffer::clearImplementationDSA;
+    } else
+    #endif
+    {
+        #ifndef MAGNUM_TARGET_GLES2
+        clearIImplementation = &AbstractFramebuffer::clearImplementationDefault;
+        clearUIImplementation = &AbstractFramebuffer::clearImplementationDefault;
+        clearFImplementation = &AbstractFramebuffer::clearImplementationDefault;
+        clearFIImplementation = &AbstractFramebuffer::clearImplementationDefault;
+        #endif
+    }
+
     /* Framebuffer texture attachment on ES3 */
     #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_WEBGL) && !defined(MAGNUM_TARGET_GLES2)
     if(context.isVersionSupported(Version::GLES320))

src/Magnum/GL/Implementation/driverSpecific.cpp

@@ -230,6 +230,10 @@ namespace {
            non-array cube map attachment works. Using the non-DSA code path as
            a workaround. */
         "intel-windows-broken-dsa-layered-cubemap-array-framebuffer-attachment",
+
+        /* DSA glClearNamedFramebuffer*() on Intel Windows drivers doesn't do
+           anything. Using the non-DSA code path as a workaournd. */
+        "intel-windows-broken-dsa-framebuffer-clear",
         #endif
 
         #ifndef MAGNUM_TARGET_GLES