Fixed build warnings on MSVC14 x64 in the LWS format sources.

code/LWSLoader.cpp

@@ -902,7 +902,7 @@ void LWSImporter::InternReadFile( const std::string& pFile, aiScene* pScene,
         anim->mTicksPerSecond = fps;
         anim->mDuration = last-(first-1); /* fixme ... zero or one-based?*/
 
-        anim->mChannels = new aiNodeAnim*[anim->mNumChannels = anims.size()];
+        anim->mChannels = new aiNodeAnim*[anim->mNumChannels = static_cast<unsigned int>(anims.size())];
         std::copy(anims.begin(),anims.end(),anim->mChannels);
     }