Added a new entry point lib/fox16.rb that hopefully will dynamically

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.

Manifest.txt

@@ -375,6 +375,7 @@ ext/fox16/treelist_wrap.cpp
 ext/fox16/ui_wrap.cpp
 ext/fox16/unregisterOwnedObjects.cpp
 index.html
+lib/fox16.rb
 lib/fox16/accel_table.rb
 lib/fox16/aliases.rb
 lib/fox16/bitmapview.rb

lib/fox16.rb

+if RUBY_PLATFORM =~ (mswin|mingw)/i
+  require "#{RUBY_VERSION.sub(/\.\d+$/, '')}/fox16.so"
+elsif RUBY_PLATFORM =~ /darwin/
+  require "fox16.bundle"
+else
+  require "fox16.so"
+end
+