[mingw] add timeops here, this contains prototypes for `gmtime_r` and `localtime_r`, which we need on windows

src/dl_fldigi/flights.cxx

@@ -19,6 +19,7 @@
 #include "fl_digi.h"
 #include "configuration.h"
 #include "confdialog.h"
+#include "timeops.h"
 
 #include "jsoncpp.h"
 #include "habitat/RFC3339.h"

src/ssdv/ssdv_rx.cxx

@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <setjmp.h>
 #include "ssdv_rx.h"
+#include "timeops.h"
 
 #include <curl/curl.h>