Fix MINGW gmtime_r() segfault and move to compat.h

mythtv/libs/libmythbase/compat.h

@@ -245,6 +245,21 @@ inline const char *dlerror(void)
 #define setuid(x)
 #endif // USING_MINGW
 
+#if defined(USING_MINGW)
+static inline struct tm *gmtime_r(const time_t *timep, struct tm *result)
+{
+    // this is safe on windows, where gmtime uses a thread local variable.
+    // using _gmtime_s() would be better, but needs to be tested on windows.
+    struct tm *tmp = gmtime(timep);
+    if (tmp)
+    {
+        *result = *tmp;
+        return result;
+    }
+    return NULL;
+}
+#endif 
+
 #ifdef USING_MINGW
 #define    timeradd(a, b, result)                       \
   do {                                                  \

mythtv/libs/libmythtv/eithelper.cpp

@@ -20,12 +20,7 @@ using namespace std;
 #include "util.h"
 #include "programdata.h"
 #include "programinfo.h" // for subtitle types and audio and video properties
-
-#ifdef USING_MINGW
-    #define gmtime_r( _clock, _result ) \
-            ( *(_result) = *gmtime( (_clock) ), \
-              (_result) )
-#endif
+#include "compat.h" // for gmtime_r on windows.
 
 const uint EITHelper::kChunkSize = 20;
 EITCache *EITHelper::eitcache = new EITCache();