[Bug c/59852] Support sparse-style __attribute__((bitwise)) (type attribute)

[hpa at zytor dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59852

--- Comment #3 from H. Peter Anvin <hpa at zytor dot com> ---
a == b and a != b are permitted.
~a is permitted iff sizeof(a) >= sizeof(int).
!a and other booleanizing operations are permitted but produces integer
(non-bitwise) results.