debian/rules: Highly enforce --no-parallel mode while Xserver is still on imake. Can be re-parallelized after autotools conversion.

Attributes GH PR #686: https://github.com/ArcticaProject/nx-libs/pull/686

Revert "debian/rules: Avoid dh_auto_build. It adds -Oline since 11.2 which let's make choke in nx-X11/ subdir on the Makefiles target. Reason unknown."

This reverts commit 94d77e27.

This reverts commit 190e3df4.

debian/rules: Drop override_dh_clean. Makefile (et al.) removal in nx-X11/ has now been moved to the distclean target.

debian/rules: Avoid dh_auto_build. It adds -Oline since 11.2 which let's make choke in nx-X11/ subdir on the Makefiles target. Reason unknown.

Makefile targets: Rewriting and consolidating the target structure for nx-X11/ subdir (except nx-X11/lib/).

Makefile: Don't do a parallel clean-up of nx-X11. We have seen failures and due to the upcoming switch to autotools, it is pointless to dive into fixing it in the Imakefile stack.

Attributes GH PR #676: https://github.com/ArcticaProject/nx-libs/pull/676

This utilizes IMAKE_DEFINES to pass down the value to UseTIRPC directly.

Fixes: ArcticaProject/nx-libs#665

nx-X11/programs/Xserver/Imakefile: move $(PIXMANLIB) to NXAGENTSYSLIBS, since libXcompext doesn't actually need it.

nx-X11/programs/Xserver/Imakefile: use printf with no trailing newline instead of echo for variable value.

nx-X11/programs/Xserver/Imakefile: drop system libraries out of target list for nxagent regeneration.

Updating timestamps on object files and libraries used to compose
nxagent is only meaningful for actual files within the buildroot.
External dependencies would be ignored anyway, and worse, cause older
GNU Make versions to fail if they contain special characters like a
percent sign, which is typically interpreted as a wild card character.

nx-X11/programs/Xserver/hw/nxagent/Screen.c: do not try to set a NULL mode if the output was disconnected before.

Fixes: ArcticaProject/nx-libs#677

nx-X11/programs/Xserver/hw/nxagent/Screen.c: initialize pointers to NULL to avoid referencing random data.

Attributes GH PR #672: https://github.com/ArcticaProject/nx-libs/pull/672

 commit cad5a1050b7184d828aef9c1dd151c3ab649d37e
 Author: Nathan Kidd <nkidd@opentext.com>
 Date:   Fri Jan 9 09:57:23 2015 -0500

    Unvalidated lengths

    v2: Add overflow check and remove unnecessary check (Julien Cristau)

    This addresses:
    CVE-2017-12184 in XINERAMA
    CVE-2017-12185 in MIT-SCREEN-SAVER
    CVE-2017-12186 in X-Resource
    CVE-2017-12187 in RENDER
Reviewed-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>
Reviewed-by: Julien Cristau <jcristau@debian.org>
Signed-off-by: Nathan Kidd <nkidd@opentext.com>
Signed-off-by: Julien Cristau <jcristau@debian.org>
Backported-to-NX-by: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>

Attributes GH PR #670: https://github.com/ArcticaProject/nx-libs/pull/670

Xserver/hw/nxagent/Screen.c: Drop commented out code. Functionality now implemented in intersect_bb() function.