Fix memory leak if ALL_STATE and multithreaded.

* localtime.c (gmtcheck) [ALL_STATE]: Don't leak memory if two
threads invoke this function nearly simultaneously.
Problem reported by Andy Heninger in:
http://mm.icann.org/pipermail/tz/2014-September/021599.html
* NEWS: Document this.

NEWS

@@ -30,6 +30,10 @@ Unreleased, experimental changes
     An access to uninitalized data has been fixed.
     (Thanks to Jörg Richter for reporting the problem.)
 
+    A memory leak has been fixed if ALL_STATE and THREAD_SAFE are defined
+    and two threads race to initialize data used by gmtime-like functions.
+    (Thanks to Andy Heninger for reporting the problem.)
+
   Changes affecting build procedure
 
     'make check' now checks better for properly-sorted data.

localtime.c

@@ -1249,12 +1249,14 @@ gmtcheck(void)
     return;
   if (lock() != 0)
     return;
+  if (! gmt_is_set) {
 #ifdef ALL_STATE
-  gmtptr = malloc(sizeof *gmtptr);
+    gmtptr = malloc(sizeof *gmtptr);
 #endif
-  if (gmtptr)
-    gmtload(gmtptr);
-  gmt_is_set = true;
+    if (gmtptr)
+      gmtload(gmtptr);
+    gmt_is_set = true;
+  }
   unlock();
 }