Context initialization was not skipping surely supported extensions.

On OpenGL 3.3 context it was checking for support of all 3.0, 3.1 and
3.2 extensions even if isExtensionSupported() didn't use that
information at all.

src/Context.cpp

@@ -239,7 +239,7 @@ Context::Context() {
         Version::None
     };
     std::size_t future = 0;
-    while(versions[future] != Version::None && !isVersionSupported(_version))
+    while(versions[future] != Version::None && isVersionSupported(versions[future]))
         ++future;
 
     /* List of extensions from future versions (extensions from current and