Avoid having our own custom stuff and instead use the modern, standard
types, for familiarity.

The generally recommended way is to include it from source files, not
headers. We had a mix of both. Let's try to be consistent and follow the
recommended way.

Make sure it can map between the key codes of the local system
in to the key codes used by the protocol.

Since it is caught by the local system on most platforms.

Remove the FLTK simple keyboard system and reorganise things in
preparation for a more direct approach.

git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4665 3789f03b-4d11-0410-bbf8-ca57d06f2519