Zsh's makepro.awk script currently pulls all the prototypes out of the
source file regardless of whether they're compiled into the image.

This causes a problem with with exec.pro, since it pulls out
prototypes for current_limits, which is in terms of the RLIM_NLIMITS
#define.  If HAVE_GETRLIMIT isn't defined, RLIM_NLIMITS probably isn't
either.  The upshot is that exec.pro doesn't compile when running
under cygwin.

It also causes a few warnings to have prototypes for static functions
that are never defined.

The fix I used was to have makepro.awk handle things like

	/**/
	#ifdef HAVE_GETRLIMIT

and spit them out in the .pro file along with the prototypes like so:

#ifdef HAVE_GETRLIMIT
extern struct rlimit current_limits[RLIM_NLIMITS];
extern struct rlimit limits[RLIM_NLIMITS];
extern int zsetlimit _((int limnum,char*nam));
extern int setlimits _((char*nam));
#endif /* HAVE_GETRLIMIT */

...which nicely avoids the problem.