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

fix retrieving of file handles, so that FXApp#addInput works with ruby 1.8.7, 1.9.2 and rubinius under Linux (win32 not tested yet)

support rubinius

add tasks for downloading and cross compilation of libfox, fxscintilla and depending libraries for win32