GCC 4.6 compatibility: no std::is_assignable.

Just disabling it, as it appears only in tests.

src/Test/AbstractQueryGLTest.cpp

@@ -66,7 +66,10 @@ void AbstractQueryGLTest::construct() {
 
 void AbstractQueryGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<SampleQuery, const SampleQuery&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<SampleQuery, const SampleQuery&>{}));
+    #endif
 }
 
 void AbstractQueryGLTest::constructMove() {

src/Test/AbstractShaderProgramGLTest.cpp

@@ -70,7 +70,10 @@ void AbstractShaderProgramGLTest::construct() {
 
 void AbstractShaderProgramGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<MyShader, const MyShader&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<MyShader, const MyShader&>{}));
+    #endif
 }
 
 void AbstractShaderProgramGLTest::constructMove() {

src/Test/AbstractTextureGLTest.cpp

@@ -61,7 +61,10 @@ void AbstractTextureGLTest::construct() {
 
 void AbstractTextureGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Texture2D, const Texture2D&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Texture2D, const Texture2D&>{}));
+    #endif
 }
 
 void AbstractTextureGLTest::constructMove() {

src/Test/BufferGLTest.cpp

@@ -91,7 +91,10 @@ void BufferGLTest::construct() {
 
 void BufferGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Buffer, const Buffer&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Buffer, const Buffer&>{}));
+    #endif
 }
 
 void BufferGLTest::constructMove() {

src/Test/BufferImageGLTest.cpp

@@ -66,7 +66,10 @@ void BufferImageTest::construct() {
 
 void BufferImageTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<BufferImage2D, const BufferImage2D&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<BufferImage2D, const BufferImage2D&>{}));
+    #endif
 }
 
 void BufferImageTest::constructMove() {

src/Test/FramebufferGLTest.cpp

@@ -62,7 +62,10 @@ void FramebufferGLTest::construct() {
 
 void FramebufferGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Framebuffer, const Framebuffer&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Framebuffer, const Framebuffer&>{}));
+    #endif
 }
 
 void FramebufferGLTest::constructMove() {

src/Test/ImageTest.cpp

@@ -64,7 +64,10 @@ void ImageTest::construct() {
 
 void ImageTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Image2D, const Image2D&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Image2D, const Image2D&>{}));
+    #endif
 }
 
 void ImageTest::constructMove() {

src/Test/MeshGLTest.cpp

@@ -61,7 +61,10 @@ void MeshGLTest::construct() {
 
 void MeshGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Mesh, const Mesh&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Mesh, const Mesh&>{}));
+    #endif
 }
 
 void MeshGLTest::constructMove() {

src/Test/RenderbufferGLTest.cpp

@@ -61,7 +61,10 @@ void RenderbufferGLTest::construct() {
 
 void RenderbufferGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Renderbuffer, const Renderbuffer&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Renderbuffer, const Renderbuffer&>{}));
+    #endif
 }
 
 void RenderbufferGLTest::constructMove() {

src/Test/ShaderGLTest.cpp

@@ -71,7 +71,10 @@ void ShaderGLTest::construct() {
 
 void ShaderGLTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Shader, const Shader&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Shader, const Shader&>{}));
+    #endif
 }
 
 void ShaderGLTest::constructMove() {

src/Trade/Test/ImageDataTest.cpp

@@ -62,7 +62,10 @@ void ImageDataTest::construct() {
 
 void ImageDataTest::constructCopy() {
     CORRADE_VERIFY(!(std::is_constructible<Trade::ImageData2D, const Trade::ImageData2D&>{}));
+    /* GCC 4.6 doesn't have std::is_assignable */
+    #ifndef CORRADE_GCC46_COMPATIBILITY
     CORRADE_VERIFY(!(std::is_assignable<Trade::ImageData2D, const Trade::ImageData2D&>{}));
+    #endif
 }
 
 void ImageDataTest::constructMove() {