Add tm_gmtoff test.

Author: michaelrsweet

configure

@@ -4724,6 +4724,41 @@ printf "%s\n" "#define HAVE_TIMEGM 1" >>confdefs.h
 fi
 
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for tm_gmtoff member in tm structure" >&5
+printf %s "checking for tm_gmtoff member in tm structure... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+    #include <time.h>
+int
+main (void)
+{
+
+        struct tm t;
+	int o = t.tm_gmtoff;
+
+  ;
+  return 0;
+}
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
+
+printf "%s\n" "#define HAVE_TM_GMTOFF 1" >>confdefs.h
+
+
+else $as_nop
+
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+
 
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for long long int" >&5
 printf %s "checking for long long int... " >&6; }

configure.ac

@@ -247,11 +247,24 @@ AC_COMPILE_IFELSE([
 ])
 
 
-dnl See if we have the timegm function...
+dnl Test date/time functionality...
 AC_CHECK_FUNC([timegm], [
     AC_DEFINE([HAVE_TIMEGM], [1], [Do we have the timegm function?])
 ])
 
+AC_MSG_CHECKING([for tm_gmtoff member in tm structure])
+AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([[#include <time.h>]], [[
+        struct tm t;
+	int o = t.tm_gmtoff;
+    ]])
+], [
+    AC_MSG_RESULT([yes])
+    AC_DEFINE([HAVE_TM_GMTOFF], [1], [Have tm_gmtoff member in struct tm?])
+], [
+    AC_MSG_RESULT([no])
+])
+
 
 dnl Check for "long long" support...
 AC_CACHE_CHECK([for long long int], [ac_cv_c_long_long], [