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

Remove some comments, to only from C++ usable methods