No real changes, just clean up sources by removing trailing spaces from
all the non-generated files.
This should hopefully avoid future commits mixing significant changes
with insignificant whitespace ones.
This basically removes the "adv" library, even though it's still
preserved for compatibility with user make/project files referring to
it.
It is done because the distinction between "adv" and "core" was never
really clear (e.g. why wxTreeCtrl was in core but wxTreeListCtrl in
adv?) and it prevented some core classes from using adv ones.
