It is faster than libjpeg and is used in MSYS2-fox as well.

.. to match the order in other cpp files.
This hopefully fixes the following build failure on FreeBSD:

compiling FXRbObjRegistry.cpp
In file included from FXRbObjRegistry.cpp:24:
In file included from ./include/FXRbCommon.h:101:
In file included from ./include/FXRuby.h:948:
./include/inlinestubs.h:80:1: error: no member named 'close' in
'FX::FXChoiceBox'
DECLARE_FXTOPWINDOW_STUBS(FXChoiceBox)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/FXRbTopWindow.h:44:23: note: expanded from macro
'DECLARE_FXTOPWINDOW_STUBS'
  return self->klass::close(notify); \
           ~~~~
Fixes #41

Since commit 54a11707 we handle arguments to blocks (callbacks) as borrowed objects and decouple
libfox objects from the corresponding FXRuby wrapper object after the call, if it's a borrowed object.
The conflict arises when the objects is already a borrowed object and is additionally passed as block argument.
In this case the object is deregistered at the end of the callback and accidently gets free'd by the GC later on.

With block arguments as dedicated object type we can differentiate between objects wrapped for one callback only and objects that are for longer use.

Fixes #39

RubyInstaller2 supports metadata tags for installation of dependent
MSYS2/MINGW libraries. The fxruby source gem requires the fox
package to be installed on the system, which the gem installer takes
care about, when this tag is set.

The feature is documented here:
https://github.com/oneclick/rubyinstaller2/wiki/For-gem-developers#msys2-library-dependency

This makes it more object orientated.

This is by design for FXRuby.h

../../../../ext/fox16_c/FXRuby.cpp: In function ‘VALUE FXRbConvertMessageData(FX::FXObject*, FX::FXObject*, FX::FXSelector, void*)’:
../../../../ext/fox16_c/FXRuby.cpp:578:17: warning: variable ‘fff’ set but not used [-Wunused-but-set-variable]
   FXInputHandle fff;
                 ^~~

../../../../ext/fox16_c/FXRuby.cpp: In function ‘VALUE FXRbMakeColorArray(const FXColor*, FX::FXint, FX::FXint)’:
../../../../ext/fox16_c/FXRuby.cpp:526:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(FXuint i=0; i<size; i++)
                   ~^~~~~

../../../../ext/fox16_c/FXRuby.cpp:91:58: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
 static const char * const safe_rb_obj_classname(VALUE obj)

On a newly created string, the string pointer points to emptystring
which is defined as static const.
When using FXString.vformat() on it, it writes a terminating zero byte
into emptystring at the first call to vsnprintf().
This results in a segfault on Windows-10 like this:

C:\WINDOWS\SYSTEM32\ntdll.dll(KiUserExceptionDispatcher+0x3a) [0x00007ff9ce169cba]
C:\WINDOWS\System32\msvcrt.dll(ungetwc+0xc74) [0x00007ff9cbf1fe04]
C:\WINDOWS\System32\msvcrt.dll(ungetwc+0xce7) [0x00007ff9cbf1fe77]
C:\WINDOWS\System32\msvcrt.dll(ungetwc+0x880) [0x00007ff9cbf1fa10]
C:\WINDOWS\System32\msvcrt.dll(vsnprintf_l+0x80) [0x00007ff9cbf1a750]
C:\WINDOWS\System32\msvcrt.dll(vsnprintf+0x11) [0x00007ff9cbf1a6c1]
C:\Ruby24-x64\lib\ruby\gems\2.4.0\gems\fxruby-1.6.35-x64-mingw32\ports\x86_64-w64-mingw32\bin\libFOX-1.6-0.dll(ZN2FX8FXString7vformatEPKcPc+0x73) [0x00000000696031bb]

The invalid memory access can be avoided by checking for an empty string
at first.

This was introduced in commit f9c2f9e4

This allows the build of fxruby on MSYS2.

within the file.

This fixes build without fxscintilla when run per 'rake compile'