Mark math.h and cmath tests as xfail on linux.

These tests were marked as failing because the libc implementation does not
use the proper return type on certain math functions. There is other weirdness
that prevents us from defining our own version of these functions.

The failing tests in cmake were separated into their own files so that the rest
failures in the rest of the cmath tests were not hidden.

This was not done for the math.h test since we don't actually supply math.h


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215275 91177308-0d34-0410-b5e6-96231b3b80d8
fix copy and pasted comment in test

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215276 91177308-0d34-0410-b5e6-96231b3b80d8
Add some extra checks to the MoveOnly test class to ensure it is not constructed or assigned from in a moved-from state.

Some tests were constructing it with 0, so use -1 as the invalid state
instead.

Reviewers: Marshall Clow

Differential Revision: http://reviews.llvm.org/D4095

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215301 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Add some extra checks to the MoveOnly test class to ensure it is not constructed or assigned from in a moved-from state."

Premature commit due to misreading CR feedback.

This reverts commit r215301.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215302 91177308-0d34-0410-b5e6-96231b3b80d8
Emulate clang atomic built-ins on gcc > 4.7

gcc 4.7 and above has atomic built-ins which slightly different APIs
from those provided by clang. Add proxy functions that wrap the gcc
built-ins to produce a symbol that is API equivalent to the clang
built-ins. This allows libc++'s atomic library to be used with gcc-4.7
and newer.

Patch contributed by Albert Wong.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215305 91177308-0d34-0410-b5e6-96231b3b80d8
NFC. Remove trailing whitespace and tabs.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215326 91177308-0d34-0410-b5e6-96231b3b80d8
Merge remote-tracking branch 'upstream/master'