- add radiant options to not load assets from
  engine path and home path, it helps people to build
  safe development environment
- add -fs_nobasepath and -fs_nohomepath to q3map2
  to do the same
- make radiant pass these options to q3map2

- add optional pakpath support
  currently an hardcoded number of 5 extra pakpath are possible
  this is still better than nothing

- if build profile use [ExtraQ3map2Args] keyword,
  radiant pass the extra pakpaths options to q3map2
  thanks to the -fs_pakpath switch that was added
  in a previous commit

gcc8: static_cast NULL instead of reinterpret_cast

See merge request xonotic/netradiant!74

Update game packs, fix some bugs to make them properly installed

See merge request xonotic/netradiant!77

Fix deprecated pango code always being used in glfont.cpp

See merge request xonotic/netradiant!78

The version check to see if the non-deprecated API is available,
PANGO_VERSION_CHECK(1,22,0), always returns false if pango-features.h
isn't included. This is because PANGO_VERSION_MAJOR, _MINOR, _MICRO
are not defined and are evaluated as 0 in the preprocessor code.

This commit fixes compiling on Debian 8 using libpango1.0-dev 1.36.8.
It was failing because deprecated function pango_ft2_get_context()
was not available (hidden in header file by PANGO_DISABLE_DEPRECATED).

Previously, game_packs_all target was just calling game_packs target, so it
was just installing free game packs, not all. It's now a proper target
setting proper environment variables before calling install-gamepacks.sh.

Previously, the install-gamepacks.sh script was looking for all
subdirectories in games/ directory for *.games directory to
copy them inside games/ directory.

So, on first run,
it was looking for games/XonoticPack/xonotic.game
to copy it as games/xonotic.game

Then on second run,
it was looking for games/XonoticPack/xonotic.game
and also for games/xonotic.game/xonotic.game
which is silly.

Now the install-gamepacks.sh script is looking for games/*Pack
subdirectories only, it means all gamepacks must end with a
capitalized Pack suffix, which is already the case and is defined
in download-gamepacks.sh after all.

- update game packs list, thanks to @NeonKnightOA
- add more workarounds for malformed gamepacks from icculus's repository
- obsolete #76