ensure intro movie is centered on linux

revert atlimit8's commit from feef4e844a1d4cc0ba6d38049ada58ac539bf4a9
I attempted to reach him/her about the reasoning for this commit but did
not get a reply.

tested on Gentoo Linux with sdl-1.2.15, sdl-gfx-2.0.24 with:
  displayWidth:    1920
  displayHeight:   1200
  baseXResolution: 640
  baseYResolution: 400

see:
https://github.com/SupSuper/OpenXcom/commit/feef4e844a1d4cc0ba6d38049ada58ac539bf4a9
https://github.com/SupSuper/OpenXcom/pull/678
https://github.com/SupSuper/OpenXcom/pull/675
http://openxcom.org/bugs/openxcom/issues/294
methods for loading modded saves post-content removal
keep track of mods installed at the time of save
add loading confirmation for saves with missing mods
delete runaway timer
fix game deletion
fix memory leak/bug regarding dogfights
fix warning in transfers
Merge pull request #805 from myk002/fix_intro_centering_on_linux

fix for bug 490: ensure intro movie is centered on linux
Added multiline textlists.
fix for OSX

cast row size explicitly as UINT for std::min comparison
allow for multiple mapsets (terror missions, bases)

hey luke, check your PMs.
size_t != unsigned int - let's hope this fixes things
Fixed UI issues with options/saves.
fix uninstalling research/country/region mods
move some terrain-specific data out of deployments

and allow definition of civilian units per terrain while we're at it

(this is a tftd requirement)

also get rid of that hackish rng in the deployment getTerrain() function
fix OSX issue
don't center on melee attacks by aliens against civilians
fix -1 situation
More size_t