Fixed build warnings on MSVC14 x64 in the limit bone weights post-process.

code/LimitBoneWeightsProcess.cpp

@@ -129,9 +129,9 @@ void LimitBoneWeightsProcess::ProcessMesh( aiMesh* pMesh)
         std::sort( vit->begin(), vit->end());
 
         // now kill everything beyond the maximum count
-        unsigned int m = vit->size();
+        unsigned int m = static_cast<unsigned int>(vit->size());
         vit->erase( vit->begin() + mMaxWeights, vit->end());
-        removed += m-vit->size();
+        removed += static_cast<unsigned int>(m-vit->size());
 
         // and renormalize the weights
         float sum = 0.0f;