Only use Clang pragma when compiling with clang.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@180678 91177308-0d34-0410-b5e6-96231b3b80d8
Use reinterpret_casts directly in place of C-style casts.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@180679 91177308-0d34-0410-b5e6-96231b3b80d8
Use static_cast.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@180680 91177308-0d34-0410-b5e6-96231b3b80d8