Added wxGetUTCTimeMillis() and wxGetUTCTimeUSec().

Fixed wxGetLocalTimeMillis() to really return the local time and provide
wxGetUTCTimeMillis() doing what this function used to do before. Closes #13610.

Also add wxGetUTCTimeUSec() for even higher resolution time stamps as it is
basically the same as wxGetUTCTimeMillis() anyhow, at least for MSW and
non-ancient Unix systems providing gettimeofday().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69837 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/stopwatch.h

@@ -105,7 +105,11 @@ long wxGetLocalTime();
 /**
     Returns the number of milliseconds since local time 00:00:00 Jan 1st 1970.
 
-    @see wxDateTime::Now(), wxLongLong
+    The use of wxGetUTCTimeMillis() is preferred as it provides a usually
+    (except for changes to the system time) monotonic clock which the local
+    time also changes whenever DST begins or ends.
+
+    @see wxDateTime::Now(), wxGetUTCTimeMillis(), wxGetUTCTimeUSec()
 
     @header{wx/stopwatch.h}
 */
@@ -120,5 +124,19 @@ wxLongLong wxGetLocalTimeMillis();
 */
 long wxGetUTCTime();
 
+/**
+    Returns the number of milliseconds since GMT 00:00:00 Jan 1st 1970.
+
+    @since 2.9.3
+ */
+wxLongLong wxGetUTCTimeMillis();
+
+/**
+    Returns the number of microseconds since GMT 00:00:00 Jan 1st 1970.
+
+    @since 2.9.3
+ */
+wxLongLong wxGetUTCTimeUSec();
+
 //@}