Need the timegm stub on Solaris

This is Solaris 10 and gcc 5.5.50 from opencsw.

src/civetweb.c

@@ -59,7 +59,7 @@
 #if defined(__linux__) && !defined(_XOPEN_SOURCE)
 #define _XOPEN_SOURCE 600 /* For flockfile() on Linux */
 #endif
-#if defined(__LSB_VERSION__)
+#if defined(__LSB_VERSION__) || defined(__sun)
 #define NEED_TIMEGM
 #define NO_THREAD_NAME
 #endif