Handle '-' consistently

In general, POSIX does not define /dev/std{in, out, err} because it
does not want to depend on the dev-filesystem.
For utilities, it thus introduced the '-'-keyword to denote standard
input (and output in some cases) and the programs have to deal with
it accordingly.

Sadly, the design of many tools doesn't allow strict shell-redirections
and many scripts don't even use this feature when possible.

Thus, we made the decision to implement it consistently across all
tools where it makes sense (namely those which read files).

Along the way, I spotted some behavioural bugs in libutil/crypt.c and
others where it was forgotten to fshut the files after use.

libutil/crypt.c

@@ -126,18 +126,24 @@ cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
 		mdprint(md, "<stdin>", sz);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if (!(fp = fopen(*argv, "r"))) {
+			if ((*argv)[0] == '-' && !(*argv)[1]) {
+				*argv = "<stdin>";
+				fp = stdin;
+			} else if (!(fp = fopen(*argv, "r"))) {
 				weprintf("fopen %s:", *argv);
 				ret = 1;
 				continue;
 			}
-			if (cryptsum(ops, fp, *argv, md) == 1)
+			if (cryptsum(ops, fp, *argv, md)) {
 				ret = 1;
-			else
+			} else {
 				mdprint(md, *argv, sz);
-			fclose(fp);
+			}
+			if (fp != stdin && fshut(fp, *argv))
+				ret = 1;
 		}
 	}
+
 	return ret;
 }