Fix mansion mapgen:

The walls to the left and bottom must not be rotated, those walls are created by every mansion
mapgen (even by the non-entrance ones). The non-entrance mansion mapgen creates them but does *not* rotate them.
To match this, the entrance should not rotate them either.

Further: made the columns in the entrance symmetrical (6 squares between
each row, not 5, matches the double door).
Fix mapgen of military outpost:

Increase the enclosed area (moved the chain link fences to outer edge of the generated area).
Check and discard overlapping rooms.
Check and fix doors leading into the wall of an adjacent room.
Fixed bug where cowboy hat costed 4 leather to make but could be cut up for 8, allowing infinite leather patches.
Change game::events into a std::list instead of vector.

Some events add new events to the list while it is being processed.
This invalidates the iterators of std::vector that are used during that processing.
Merge branch 'infinite_hats' of https://github.com/BeigeSand/Cataclysm-DDA into merge
Merge branch 'fix-event-iterator-bug' of https://github.com/BevapDin/Cataclysm-DDA into merge
Fix spawn-targeting typo

Probably not critical, but it was there.