Remove optreset from src/port/ implementations of getopt and getopt_long.

We don't actually need optreset, because we can easily fix the code to
ensure that it's cleanly restartable after having completed a scan over the
argv array; which is the only case we need to restart in.  Getting rid of
it avoids a class of interactions with the system libraries and allows
reversion of my change of yesterday in postmaster.c and postgres.c.

Back-patch to 8.4.  Before that the getopt code was a bit different anyway.

src/port/getopt_long.c

@@ -38,17 +38,21 @@
 
 #include "getopt_long.h"
 
-#ifndef HAVE_INT_OPTRESET
-int			optreset;
-
-/* else the "extern" was provided by getopt_long.h */
-#endif
-
 #define BADCH	'?'
 #define BADARG	':'
 #define EMSG	""
 
 
+/*
+ * getopt_long
+ *	Parse argc/argv argument vector, with long options.
+ *
+ * This implementation does not use optreset.  Instead, we guarantee that
+ * it can be restarted on a new argv array after a previous call returned -1,
+ * if the caller resets optind to 1 before the first call of the new series.
+ * (Internally, this means we must be sure to reset "place" to EMSG before
+ * returning -1.)
+ */
 int
 getopt_long(int argc, char *const argv[],
 			const char *optstring,
@@ -57,10 +61,8 @@ getopt_long(int argc, char *const argv[],
 	static char *place = EMSG;	/* option letter processing */
 	char	   *oli;			/* option letter list index */
 
-	if (optreset || !*place)
+	if (!*place)
 	{							/* update scanning pointer */
-		optreset = 0;
-
 		if (optind >= argc)
 		{
 			place = EMSG;