Fixed warnings on redefine keywords and reserved ids.

Repared support for warnings -Wkeyword-macro and -Wreserved-id-macro.
The warning -Wkeyword-macro now is not issued in patterns that are used
in configuration scripts:

    #define inline

also for 'const', 'extern' and 'static'. If macro repalcement is identical
to macro name, the warning also is not issued:

    #define volatile volatile

And finally if macro replacement is also a keyword identical to the replaced
one but decorated with leading/trailing underscores:

    #define inline __inline
    #define inline __inline__
    #define inline _inline // in MSVC compatibility mode

Warning -Wreserved-id-macro is off by default, it could help catching
things like:

    #undef __cplusplus


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@224512 91177308-0d34-0410-b5e6-96231b3b80d8