Allow %' to be used as a format flag by printf(1). This makes it

possible to print the thousands separator in the locale setups that
have one, by something like this:

    $ env -i LC_NUMERIC=en_US.ISO8859-1 ./printf "%'0.2f\n" 12345
    12,345.00

Reviewed by:	das

usr.bin/printf/printf.c

@@ -138,7 +138,7 @@ main(int argc, char *argv[])
 	 * arguments, arguments of zero/null string are provided to use
 	 * up the format string.
 	 */
-	skip1 = "#-+ 0";
+	skip1 = "#'-+ 0";
 	skip2 = "0123456789";
 
 	chopped = escape(fmt = format = *argv, 1);/* backslash interpretation */