pythonPackages.matplotlib: Update to use buildPythonPackage

Matplotlib is currently using hacked together build / install phases
which mimick this functionality of buildPythonPackage. This patch
changes the expression to remove the duplicated build scripting.
network-manager-applet: re-do schema generation

fixes #1355. partial revert of f4d4e12c (introduced by #1313).

meta.priority is set to 6 (lower priority than standard) to resolve the
conflict of an exported gschemas.compiled for evince as for nm-applet.
this linked file is NOT consulted, as both binaries are wrapped to look
for their schemas in their nix store path first.

a better fix would avoid already avoid linking those gschemas.compiled
files into the environment.
add dvtm 0.10
add kde-gtk-config-2.2.1
xonotic: compile the glx version and add a symlink to default to the sdl
version.
Added Nexuiz-2.5.2.
add qtcurve-1.8.17
oraclejre7: Add package (as a variant of oraclejdk7)
saneBackends: Update to 1.0.24
pngcrush: update from 1.7.69 to 1.7.70
elixir: update from 0.11.2 to 0.12.0
Merge pull request #1449 from wizeman/u/sane

saneBackends: Update to 1.0.24
Merge pull request #1439 from iyzsong/dvtm

add dvtm 0.10
Merge pull request #1440 from rszibele/nexuiz

Added Nexuiz-2.5.2.
Merge pull request #1441 from rszibele/xonotic

xonotic: compile the glx version and add a symlink to default to the sdl version.
Merge pull request #1445 from wizeman/u/oraclejre7

oraclejre7: Add package (as a variant of oraclejdk7)
Whitespace fixes in package expressions I maintain
networkmanager: register PPTP service
networkmanager-pptp: fix checksum
Set chunksync package's NIX_LDFLAGS to "-lgcc_s"

This works around the pthread_cancel issue