fix getopt handling of initial '+' in optstring

in the case where an initial '+' was passed in optstring (a
getopt_long feature to suppress argv permutation), getopt would fail
to see a possible subsequent ':', resulting in incorrect handling of
missing arguments.

src/misc/getopt.c

@@ -55,7 +55,7 @@ int getopt(int argc, char * const argv[], const char *optstring)
 		optpos = 0;
 	}
 
-	if (optstring[0] == '-')
+	if (optstring[0] == '-' || optstring[0] == '+')
 		optstring++;
 
 	i = 0;