systemd compat for doas

[Ted Unangst]

If the username starts with a digit, but isn't a number, treat it like root.

Index: doas.c
===================================================================
RCS file: /cvs/src/usr.bin/doas/doas.c,v
retrieving revision 1.72
diff -u -p -r1.72 doas.c
--- doas.c      27 May 2017 09:51:07 -0000      1.72
+++ doas.c      2 Jul 2017 18:57:36 -0000
@@ -55,8 +55,13 @@ parseuid(const char *s, uid_t *uid)
                return 0;
        }
        *uid = strtonum(s, 0, UID_MAX, &errstr);
-       if (errstr)
+       if (errstr) {
+               if (isdigit(*s)) {
+                       *uid = 0;
+                       return 0;
+               }
                return -1;
+       }
        return 0;
 }