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)

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

Allow more consistent read/write access to image data, that is also
usable with derived classes like FXJPGImage.

Moreover much faster String based access to the pixel data is possible,
now.

FXImage#data and FXMemoryBuffer is now deprecated.

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

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

noticed at FXComboBox#fillItems

"lyle@lylejohnson.name" in all SWIG interface files.