question about timestamp

Is there a reason that the value of the HAVE_INT64_TIMESTAMP macro is
used to choose a datatype in datetime.c instead of having a typedef
defined?

I would like to write a patch to change constructs like the following:

#ifdef HAVE_INT64_TIMESTAMP   int64       span1,               span2;
#else   double      span1,               span2;
#endif

to something like the following:
   timestamp_t span1, span2;

where timestamp_t is in some header (likely utils/datetime.h) like:

Is there a reason that the value of the HAVE_INT64_TIMESTAMP macro is
used to choose a datatype in datetime.c instead of having a typedef
defined?

I would like to write a patch to change constructs like the following:

#ifdef HAVE_INT64_TIMESTAMP   typedef int64 timestamp_t;
#else   typedef double timestamp_t,
#endif


Is this a patch like that would be welcome?

Thanks,
wt