Prevent segfault when descending stairs by not dereferencing closest_city when null.
Merge pull request #227 from Shoes01/master

Bionic fix, and a typo
Merge pull request #229 from GlyphGryph/plastic_jug_to_gallon_jug
Merge pull request #190 from tasetase/freq
Monster Picker
Fixed ridiculously stupid overmap corruption/crash bug.
Centering and bordering.
Adapting new monster group code.
TERMX/Y, VIEWX/Y are now global. More centering.
Merge commit 'bc9b0f9' into dda-master
Merge commit 'cababa6' into dda-master
Spelling correction.
Add a category flag to mtypes.
Add classic flag to overmap specials.
Add classic zombies option.
Refactor MonsterGroupManager::GetMonsterFromGroup() to allways accept a reference to the mtype vector.
Suppress non-classic monsters and locations if classic zombie mode is enabled.
Disable eyebot/copbot event from triggering in classic zombie mode.
Alow wider-screen windows.
Updated to new monster group code.
Added new crafting recipes for clothing added in the body temp mod