Remove redundant declarations of getopt(3) externals (since <unistd.h> does

take care of them), and add __FreeBSD__ to the defined() checks for the
_PATH_DIVNAME.

usr.bin/m4/main.c

@@ -146,9 +146,6 @@ struct keyblk keywrds[] = {	/* m4 keywords to be installed */
 
 #define MAXKEYS	(sizeof(keywrds)/sizeof(struct keyblk))
 
-extern int optind;
-extern char *optarg;
-
 #define MAXRECORD 50
 static struct position {
 	char *name;

usr.bin/m4/pathnames.h

@@ -50,7 +50,8 @@
 #define	UNIQUE		3			/* unique char location */
 #endif
 
-#if defined(unix) || defined(__NetBSD__) || defined(__OpenBSD__)
+#if defined(unix) || defined(__FreeBSD__) || defined(__NetBSD__) || \
+	defined(__OpenBSD__)
 #define _PATH_DIVNAME	"/tmp/m4.0XXXXXXXXXX"	/* unix diversion files */
 #define UNIQUE		8			/* unique char location */
 #endif