... 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.
... for wxString and wxArrayStringEx, holding file extensions (without dot);
to be replaced later with different types
(not yet using std::vector, becase of some uses of wxArrayString::Index with
two arguments)
And simplify some constructions of arrays
... which will make it easier to change the types of those containers to
std::vectors of other string-like classes
for wxString,
IsEmpty => empty
Clear => clear
Alloc => reserve
for wxArrayString,
Count => size
GetCount => size
IsEmpty => empty
Add => push_back
Clear => clear
Empty => clear
Sort => std::sort (only with default comparator)
SetCount => resize
Last => back
Item => operator []
Alloc => reserve
