Issue #80 - De-unify dom/media part 1

This de-unifies up to and including dom/media/platforms with the exception of
dom/media/platforms/wmf, because that one throws weird errors in the Win
SDK which don't have a clear cause (yet)

dom/media/MediaDecoder.cpp

@@ -788,6 +788,13 @@ MediaDecoder::CallSeek(const SeekTarget& aTarget, dom::Promise* aPromise)
            &MediaDecoder::OnSeekResolved, &MediaDecoder::OnSeekRejected));
 }
 
+// GetCurrentTime is defined in winbase.h as a zero argument macro forwarding to
+// GetTickCount(), which conflicts with the MediaDecoder::GetCurrentTime
+// implementation here. Clear the macro.
+#ifdef GetCurrentTime
+#undef GetCurrentTime
+#endif
+
 double
 MediaDecoder::GetCurrentTime()
 {