compat UPDATE support for timegm
diff --git a/compat/compat.h.in b/compat/compat.h.in
index c697d6c..6df7a7b 100644
--- a/compat/compat.h.in
+++ b/compat/compat.h.in
@@ -70,6 +70,7 @@
 #cmakedefine HAVE_REALPATH
 #cmakedefine HAVE_LOCALTIME_R
 #cmakedefine HAVE_GMTIME_R
+#cmakedefine HAVE_TIMEGM
 #cmakedefine HAVE_STRPTIME
 #cmakedefine HAVE_MMAP
 #cmakedefine HAVE_DIRNAME
@@ -188,6 +189,14 @@
 struct tm *localtime_r(const time_t *timep, struct tm *result);
 #endif
 
+#ifndef HAVE_TIMEGM
+# if defined (_WIN32)
+#  define timegm _mkgmtime
+# else
+#  error No timegm() implementation for this platform is available.
+# endif
+#endif
+
 #ifndef HAVE_STRPTIME
 char *strptime(const char *s, const char *format, struct tm *tm);
 #endif