allow for strftime() %Z timezone to be >4 chars

In create_long_time_string(), the strftime() buffer reserves 4 bytes
for the %Z timezone abbreviation.  This limit is insufficient for some
locales (eg, "GMT-1").  The zoneinfo database shows some as long as
8 characters.

This increases the strftime() buffer to 32 bytes which reserves 11
bytes for the %Z timezone.

Fixes issue 16.

util-str.c

@@ -254,7 +254,7 @@ char * create_long_time_string(time_t t)
 {
     char *p;
     struct tm tm;
-    const int len = 25;                 /* YYYY-MM-DD HH:MM:SS ZONE + NUL */
+    const int len = 32;
 
     if (!(p = malloc(len))) {
         out_of_memory();