Fix naming mismatch of allocator functions.

Allocator functions that take file/line/func parameters are prefixed
with single-underscore when MALLOC_DEBUG is not defined,
double-underscore when it is defined.  This change updates all
allocators that accept file/line/func to have the same prototype in
either ABI mode.  The parameter order of __ast_vasprintf and
__ast_asprintf in utils.h have been changed to match that of astmm.h.

End-use allocator macro's have been removed from astmm.h and moved to an
unconditional part of utils.h.

Change-Id: I823bb6ce2b5675b3a4735948f10a3b420e9a023a