Merging r196212:
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r196212 | alp | 2013-12-02 22:13:01 -0800 (Mon, 02 Dec 2013) | 22 lines

Emit an extension warning when changing system header tokens

clang converts keywords to identifiers for compatibility with various system
headers such as GNU libc.

Implement a -Wkeyword-compat extension warning to diagnose those cases. The
warning is on by default but will generally be ignored in system headers. It
can however be enabled globally to aid standards conformance testing.

This also changes the __uptr keyword avoidance from r195710 to no longer
special-case system headers, bringing it in line with other similar workarounds
in clang.

Implementation returns bool for symmetry with token annotation functions.

Some examples:

warning: keyword '__is_pod' will be treated as an identifier for the remainder of the translation unit [-Wkeyword-compat]
struct __is_pod

warning: keyword '__uptr' will be treated as an identifier here [-Wkeyword-compat]
union w *__uptr;
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Merging r-196802:
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r196802 | chandlerc | 2013-12-09 11:25:51 -0800 (Mon, 09 Dec 2013) | 11 lines

Revert three patches which were committed without explicit contribution
by their authors.

This may break builds where others added code relying on these patches,
but please *do not* revert this commit. Instead, we will prepare patches
which fix the failures.

Reverts the following commits:
r168306: "[asan] support x32 mode in the fast stack unwinder. Patch by H.J. Lu"
r168356: "[asan] more support for powerpc, patch by Peter Bergner"
r196489: "[sanitizer] fix the ppc32 build (patch by Jakub Jelinek)"
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