previous swig's #setData implementation wasn't really useable

Calling other classes while garbage collection is generally dangerous and useless.

This happens with FXFileSelector.

FXWindow destructor calls recalc() and changeFocus() of it's parent windows.
Since these methods are routed back to Ruby code, but calling Ruby code from
GC isn't a good idea, we mark the parent window as "in_gc", so that it will
ignore recalc() and changeFocus() calls completely.

The parent window should also be scheduled to be free'd. In the other case,
the child window would have been marked as used.

whitespaces

Calling any Ruby code within the mark phase is generelly dangerous,
because it usually allocates some objects.
Since most of the methods of FX objects can be overloaded in Ruby,
the calls in markfuncs now call explizitly the C++ methods.

Also remove some double marking of objects.

Replace PLATFORM with RUBY_PLATFORM and respect other platforms, too. Fixes http://rubyforge.org/tracker/index.php?func=detail&aid=28740&group_id=300&atid=1223

change unconditional LIBZ_MAKEFILE task to a file task - the configure needs to be started only once

change build dependencies so that (cross) compile and gem tasks no longer need the explicit configure task

change zlib URL to Sourceforge, because on zlib.net older versions are immediately dropped, as soon as a new version was released

This could hide namespace issues in fxruby.

The target objects stored in the accelerator table are currently
private. Therefore FXRbAccelTable::markfunc() doesn't mark them as used.
As a workaround the objects are additionally stored in @targets Hash.

Conflicts:
	ext/fox16/FXRuby.cpp

The Ruby String buffer was free'd by GC and FXMemoryStream#close

noticed at FXComboBox#fillItems