GCC 4.6 compatibility: no std::unordered_map::emplace().

Basically reverts (only for GCC 4.6) what was done in
b9b690b611.

src/Context.cpp

@@ -337,7 +337,11 @@ Context::Context() {
     std::unordered_map<std::string, Extension> futureExtensions;
     for(std::size_t i = future; i != versions.size(); ++i)
         for(const Extension& extension: Extension::extensions(versions[i]))
+            #ifndef CORRADE_GCC46_COMPATIBILITY
             futureExtensions.emplace(extension._string, extension);
+            #else
+            futureExtensions.insert({extension._string, extension});
+            #endif
 
     /* Check for presence of extensions in future versions */
     #ifndef MAGNUM_TARGET_GLES2

src/MeshTools/RemoveDuplicates.h

@@ -127,7 +127,11 @@ template<class Vertex, std::size_t vertexSize> void RemoveDuplicates<Vertex, ver
                exists, change vertex pointer of the face to already
                existing vertex */
             HashedVertex v(*it, table.size());
+            #ifndef CORRADE_GCC46_COMPATIBILITY
             auto result = table.emplace(Math::Vector<vertexSize, std::size_t>::from(index), v);
+            #else
+            auto result = table.insert({Math::Vector<vertexSize, std::size_t>::from(index), v});
+            #endif
             *it = result.first->second.newIndex;
         }
 

src/ResourceManager.h

@@ -469,7 +469,11 @@ template<class T> void ResourceManagerData<T>::set(const ResourceKey key, T* con
 
     /* Insert it, if not already here */
     } else if(it == _data.end())
+        #ifndef CORRADE_GCC46_COMPATIBILITY
         it = _data.emplace(key, Data()).first;
+        #else
+        it = _data.insert({key, Data()}).first;
+        #endif
 
     /* Replace previous data */
     delete it->second.data;