options: Change ast_options from ast_flags to ast_flags64.

options:  Change ast_options from ast_flags to ast_flags64.

DeveloperNote: The 32-bit ast_options has no room left to accomodate new
options and so has been converted to an ast_flags64 structure. All internal
references to ast_options have been updated to use the 64-bit flag
manipulation macros.  External module references to the 32-bit ast_options
should continue to work on little-endian systems because the
least-significant bytes of a 64 bit integer will be in the same location as a
32-bit integer.  Because that's not the case on big-endian systems, we've
swapped the bytes in the flags manupulation macros on big-endian systems
so external modules should still work however you are encouraged to test.

(cherry picked from commit d1a194596756250a68d5de8ab7dd805640be3558)