Mark some more non-literal options

In the usage section of varnishstat, some non-literal options were not
caught by the backport.

bin/varnishstat/varnishstat.c

@@ -251,7 +251,7 @@ usage(void)
 {
 #define FMT "    %-28s # %s\n"
 	fprintf(stderr, "usage: varnishstat "
-	    "[-1lV] [-f field] [-t seconds|<off>] "
+	    "[-1lV] [-f <glob>] [-t <seconds>|<off>] "
 	    VSC_n_USAGE "\n");
 	fprintf(stderr, FMT, "-1", "Print the statistics to stdout.");
 	fprintf(stderr, FMT, "-f <glob>", "Field inclusion glob");
@@ -259,11 +259,11 @@ usage(void)
 	    "If it starts with '^' it is used as an exclusion list.");
 	fprintf(stderr, FMT, "-l",
 	    "Lists the available fields to use with the -f option.");
-	fprintf(stderr, FMT, "-n varnish_name",
+	fprintf(stderr, FMT, "-n <varnish_name>",
 	    "The varnishd instance to get logs from.");
-	fprintf(stderr, FMT, "-N filename",
+	fprintf(stderr, FMT, "-N <filename>",
 	    "Filename of a stale VSM instance.");
-	fprintf(stderr, FMT, "-t seconds|<off>",
+	fprintf(stderr, FMT, "-t <seconds>|<off>",
 	    "Timeout before returning error on initial VSM connection.");
 	fprintf(stderr, FMT, "-V", "Display the version number and exit.");
 	fprintf(stderr, FMT, "-x",