This fixes issue #10.

Stacktrace was:
==4561== Invalid read of size 8
==4561==    at 0x4F726FF: st_lookup (st.c:414)
==4561==    by 0x4FCEAD6: rb_method_entry_get_without_cache (vm_method.c:182)
==4561==    by 0x4FD94E5: rb_funcall (vm_eval.c:315)
==4561==    by 0x810DAF2: FXRbCallVoidMethod(FX::FXObject*, unsigned long) (in /home/lars/.rvm/gems/ruby-2.0.0-p247/gems/fxruby-1.6.28/lib/fox16_c.so)
==4561==    by 0x81AC98E: FXRbTreeList::recalc() (in /home/lars/.rvm/gems/ruby-2.0.0-p247/gems/fxruby-1.6.28/lib/fox16_c.so)
==4561==    by 0x8FC78DC: FX::FXTreeList::removeItems(FX::FXTreeItem*, FX::FXTreeItem*, unsigned char) (FXTreeList.cpp:2340)
==4561==    by 0x8FC7916: FX::FXTreeList::removeItem(FX::FXTreeItem*, unsigned char) (FXTreeList.cpp:2347)
==4561==    by 0x829ED0F: FXRbTreeItem::freefunc(FX::FXTreeItem*) (in /home/lars/.rvm/gems/ruby-2.0.0-p247/gems/fxruby-1.6.28/lib/fox16_c.so)
==4561==    by 0x4EBA505: finalize_list (gc.c:1415)
==4561==    by 0x4EC15A3: rb_gc_call_finalizer_at_exit (gc.c:1552)
==4561==    by 0x4EA8064: ruby_cleanup (eval.c:127)
==4561==    by 0x4EA8292: ruby_run_node (eval.c:307)
==4561==  Address 0x74fb894853ff8550 is not stack'd, malloc'd or (recently) free'd
==4561==
segfault_on_close.rb: [BUG] Segmentation fault

So we need to use it properly too.

See bug https://bugs.ruby-lang.org/issues/6504#change-38019

Update cross compilation tasks to build x64 and x86 targets.

Conflicts:
	Rakefile

Before commit af543822 loading order of fox16.so and fox16.rb was irrelevant.
But now fox16.rb must be called, in order to load ruby files to the C++
extension. Renaming the C++ extension ensures, that fox16.rb is called first.

With the flag set, the icon would be free'd twice, first by the FXSplashWindow
and then by Ruby's GC.

The internal object allocated when calling FXSplashWindow.new was FXSplashWindow instead
of FXRbSplashWindow, so that no FXRbUnregisterRubyObj() was called. Therefore the object
was double free'd.

Stacktrace was:
==11529== Invalid read of size 8
==11529==    at 0x9265BBC: FX::FXObject::getClassName() const (FXObject.cpp:280)
==11529==    by 0x862EE55: FXRbObject::freefunc(FX::FXObject*) (markfuncs.cpp:77)
==11529==    by 0x4EA6254: finalize_list (gc.c:2944)
==11529==    by 0x4EAAFC2: rb_gc_call_finalizer_at_exit (gc.c:3075)
==11529==    by 0x4E9773B: ruby_cleanup (eval.c:101)
==11529==    by 0x4E979C4: ruby_run_node (eval.c:244)
==11529==    by 0x4007FA: main (main.c:38)
==11529==  Address 0x75e24c0 is 0 bytes inside a block of size 248 free'd
==11529==    at 0x4C2A4BC: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11529==    by 0x92B98AD: FX::FXSplashWindow::~FXSplashWindow() (FXSplashWindow.cpp:219)
==11529==    by 0x917C990: FX::FXComposite::~FXComposite() (FXComposite.cpp:304)
==11529==    by 0x929A5EF: FX::FXRootWindow::~FXRootWindow() (FXRootWindow.cpp:209)
==11529==    by 0x929A621: FX::FXRootWindow::~FXRootWindow() (FXRootWindow.cpp:211)
==11529==    by 0x9156DB9: FX::FXApp::~FXApp() (FXApp.cpp:4994)
==11529==    by 0x84912F3: FXRbApp::~FXRbApp() (FXRbApp.cpp:118)
==11529==    by 0x8491347: FXRbApp::~FXRbApp() (FXRbApp.cpp:127)
==11529==    by 0x862EF8E: FXRbObject::freefunc(FX::FXObject*) (markfuncs.cpp:92)
==11529==    by 0x4EA6254: finalize_list (gc.c:2944)
==11529==    by 0x4EAAFC2: rb_gc_call_finalizer_at_exit (gc.c:3075)
==11529==    by 0x4E9773B: ruby_cleanup (eval.c:101)

Don't include sys/time.h for cross compilation, this avoids the fix for incompatible types of gettimeofday()

Avoid Segfauls in lots of methods when called with nil instead of FXApp, FXComposite or FXWindow objects