... because the two macros have the same expansion, and are both checked for
in the --keyword arguments passed to msgfmt by locale/update_po_files.sh.
This commit makes ONLY such changes, and comments in Internat.h. It is big
but quite harmless.
The intention is to introduce a type distinction in a later release, by defining
XXO differently. XXO is used where & characters in strings (for hotkeys of menu
items or control prompts) are permitted, XO where not.
... And corrected improper connections in HistoryWindow and ContrastDialog,
improper because they got called with the wrong this pointer, to
the control instead of the dialog. But that was harmless anyway because the
handlers did not use this.
... Unnecessary because transitively included.
But each .cpp file still includes its own .h file near the top to ensure
that it compiles indenendently, even if it is reincluded transitively later.
... except Audacity.h
This forces us to make each header contain all forward declarations or nested
headers that it requires, rather than depend on context.
... except Audacity.h; and in no others.
Do so even if Experimental.h gets multiply included, as in both the .h and
.cpp files.
This makes it easier to do a text scan to be sure there are no unintended quiet
changes of meaning because of omission of Experimental.h when the flag is
an enabled one.
Also move inclusions of Experimental.h earlier.
Also don't require Experimental.h to be preceded by Audacity.h to define
EXPERIMENTAL_MIDI_OUT correctly.
