Modified ROCKET_BREAK to use __debugbreak() on windows for x64 compiles.
Fix compilation warnings

Source/Core/FontDatabase.cpp: In member function ‘void* Rocket::Core::FontDatabase::LoadFace(const String&)’:
Source/Core/FontDatabase.cpp:257:10: warning: converting ‘false’ to pointer type ‘void*’ [-Wconversion-null]
   return false;

Source/Core/TextureResource.cpp: In member function ‘bool Rocket::Core::TextureResource::Load(Rocket::Core::RenderInterface*) const’:
Source/Core/TextureResource.cpp:165:70: warning: passing NULL to non-pointer argument 1 of ‘std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = long long unsigned int; _T2 = Rocket::Core::Vector2<int>]’ [-Wconversion-null]
     texture_data[render_interface] = TextureData(NULL, Vector2i(0, 0));
                                                                      ^
Source/Core/TextureResource.cpp:177:68: warning: passing NULL to non-pointer argument 1 of ‘std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = long long unsigned int; _T2 = Rocket::Core::Vector2<int>]’ [-Wconversion-null]
   texture_data[render_interface] = TextureData(NULL, Vector2i(0, 0));
Merge pull request #106 from viciious/warnings_fix

Fix compilation warnings
Merge pull request #102 from dougbinks/master

Windows x64 compatible ROCKET_BREAK
Fix gcc compilation warnings

Mostly 'converting to non-pointer type int from NULL' and vice versa
Move ElementStyleCache.* to Core
More fixes for compilation warnings
Do not precalculate kerning for all characters

Precalculating kerning for all character pairs consumed a lot of RAM (N*N complexity). For CJK fonts that contain tens thousands of glyphs it was a highly unpractical approach resulting libRocket consuming >1.5GB of RAM. Instead, encapsulate FT_Get_Kerning call in FontFaceHandle::GetKerning and let FreeType handle the kerning on the fly. In my measurements, the performance difference is negligible, especially when compiled compiled geometry is utilized.
Merge remote-tracking branch 'remotes/lloydw/master' into kerning_footprint_reduce
Merge remote-tracking branch 'remotes/origin/fixwarnings'