Patch by Howard. First part of fix for PR18218; add type traits needed to do the right thing. Fix the problems in PR18218 for isnan and pow - they also need to be applied to the other functions in <cmath>. Also, a drive-by fix for the test - now actually calls test_abs()

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@198431 91177308-0d34-0410-b5e6-96231b3b80d8
Rename ___make_pair_return to __make_pair_return_impl; ___make_tuple_return to __make_tuple_return_impl; and ____iterator_traits to __iterator_traits_impl. Part of a campaign to remove > 2 underscores from libc++. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@198457 91177308-0d34-0410-b5e6-96231b3b80d8
Implement the functions: clz, clzl, clzll, ctz, ctzl, and ctzll
for libcxx when compiled with Visual C++ on Win32 and Win64.

clang and gcc (MinGW) compilers provide these implementations themselves.



git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@198481 91177308-0d34-0410-b5e6-96231b3b80d8
80 cols fixes.



git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@198482 91177308-0d34-0410-b5e6-96231b3b80d8