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.

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.

whitespaces

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

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.

determine which shared library to load.

If RUBY_PLATFORM says we're on Windows, this loader will look under
a version-specific directory to try to load the extension. For other
platforms, it will just load the appropriate shared library from
the current directory.