STL binary Export should write 4-byte floats for vertex and normal coordinates

The STL binary format uses 4-byte floats. When using double-precision builds of Asset Importer, the STL exporter was writing out 8-byte double values instead..

code/STLExporter.cpp

@@ -172,12 +172,16 @@ void STLExporter :: WriteMeshBinary(const aiMesh* m)
             }
             nor.Normalize();
         }
-        ai_real nx = nor.x, ny = nor.y, nz = nor.z;
+        // STL binary files use 4-byte floats. This may possibly cause loss of precision
+        // for clients using 8-byte doubles
+        float nx = (float) nor.x;
+        float ny = (float) nor.y;
+        float nz = (float) nor.z;
         AI_SWAP4(nx); AI_SWAP4(ny); AI_SWAP4(nz);
         mOutput.write((char *)&nx, 4); mOutput.write((char *)&ny, 4); mOutput.write((char *)&nz, 4);
         for(unsigned int a = 0; a < f.mNumIndices; ++a) {
             const aiVector3D& v  = m->mVertices[f.mIndices[a]];
-            ai_real vx = v.x, vy = v.y, vz = v.z;
+            float vx = (float) v.x, vy = (float) v.y, vz = (float) v.z;
             AI_SWAP4(vx); AI_SWAP4(vy); AI_SWAP4(vz);
             mOutput.write((char *)&vx, 4); mOutput.write((char *)&vy, 4); mOutput.write((char *)&vz, 4);
         }