Attributes GH PR #8: https://github.com/ArcticaProject/nx-libs/pull/8

Cherry-picked from branch 3.5.0.x.

Cherry-picked from branch 3.5.0.x.

Cherry-picked from branch 3.5.0.x.

This is basically a merge of the most current xorg-server (1.17.1) code
into nx-X11.

It makes sure that for source pictures, which do not have a drawable
surface, a filter is selected that is supported on the "main" and all
other screens.  Alternatively, if the requested filter is not available
on all screens and the picture is a source picture, this function fails
gracefully.

Additionally, the ChangePictureFilter hook is now called for non-source
pictures.

This also needs an implementation in mipict.{c,h}. The default hook does
nothing and returns a success value.

nxcomp{,ext,shad}: only use the first three numbers in the full version for current_version on OS X. ld(1) on 10.6 fails otherwise.

Cherry-picked from branch 3.5.0.x.

Cherry-picked from branch 3.5.0.x.

Conflicts:
  debian/changelog

nxcomp{,ext,shad}: use the correct library naming scheme on OS X. It differs from other UNIX-based systems.

library clean-up: Don't build libNX_Xpm anymore. Use system's libXpm shared library.

 One release goal for version 3.6.x of nx-libs is dropping as many bundled libraries as possible that haven't 
 been adapted to nx-libs.

 Starting with libNX_Xpm here.

 The libNX_Xpm library is only referenced once (nx-X11/programs/Xserver/hw/nxagent/Holder.c).
 When grepping through Xserver/hw/nxagent the suspicion comes up, that the libXpm linkage is not
 needed at all, because none of the provided functions are used inside the nxagent Xserver.