More uses of AUDACITY_DLL_API...

... in many places where the function call will later need to be between
modules (or libraries, or the executable) and the annotation will be a necessity
to keep the linkage working on Windows.

That's all that this sweeping commit does.

images/Cursors.h

@@ -30,4 +30,5 @@
 #endif
 #include "Cursors32/SubViewsCursor.xpm"
 
+AUDACITY_DLL_API
 std::unique_ptr<wxCursor> MakeCursor(int WXUNUSED(CursorId), const char * const pXpm[36], int HotX, int HotY);