Fix bitfieldInsert according to GLSL spec

"bitfieldInsert inserts the bits least significant bits of insert into base at offset offset..."

glm/detail/func_integer.inl

@@ -269,7 +269,7 @@ namespace detail
 		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_integer, "'bitfieldInsert' only accept integer values");
 
 		T const Mask = static_cast<T>(detail::mask(Bits) << Offset);
-		return (Base & ~Mask) | (Insert & Mask);
+		return (Base & ~Mask) | ((Insert << static_cast<T>(Offset)) & Mask);
 	}
 
 	// bitfieldReverse