bintrans: disable argument permutation for qp and base64

Err on the side of caution and revert to the BSD-style getopt(3)
behavior for argument processing, as it's harder to go back and it's
not clear that this was strictly intentional.

This is the difference between allowing `base64 /COPYRIGHT -w 80` and
forcing `base64 -w 80 /COPYRIGHT`.

Reviewed by:	emaste, pstef
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D48483

usr.bin/bintrans/bintrans.c

@@ -139,7 +139,7 @@ base64_encode_or_decode(int argc, char *argv[])
 		{NULL,		no_argument,		NULL, 0}
 	};
 
-	while ((ch = getopt_long(argc, argv, "diw:", opts, NULL)) != -1)
+	while ((ch = getopt_long(argc, argv, "+diw:", opts, NULL)) != -1)
 		switch (ch) {
 		case 'd':
 			decode = true;

usr.bin/bintrans/qp.c

@@ -181,7 +181,7 @@ main_quotedprintable(int argc, char *argv[])
 		{NULL,		no_argument,		NULL, 0}
 	};
 
-	while ((ch = getopt_long(argc, argv, "do:ru", opts, NULL)) != -1) {
+	while ((ch = getopt_long(argc, argv, "+do:ru", opts, NULL)) != -1) {
 		switch(ch) {
 		case 'o':
 			fpo = fopen(optarg, "w");