Improve the way base64 mode is enabled based on the program name,

so that it works when the path to b64encode is used to run it.

usr.bin/uuencode/uuencode.c

@@ -58,6 +58,7 @@ __FBSDID("$FreeBSD$");
 #include <netinet/in.h>
 
 #include <err.h>
+#include <libgen.h>
 #include <resolv.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -83,7 +84,7 @@ main(int argc, char *argv[])
 	base64 = 0;
 	outfile = NULL;
 
-	if (strcmp(argv[0], "b64encode") == 0)
+	if (strcmp(basename(argv[0]), "b64encode") == 0)
 		base64 = 1;
 
 	while ((ch = getopt(argc, argv, "mo:")) != -1) {