Add fps limiter for background window.
Background fps limit should not be 0 (possible div by 0).
Fix gcc compiler warnings from -Wall, including:

unused variables or methods (-Wunused)
uninitialized variables (-Wuninitialized)
signed/unsigned comparisons (-Wsign-compare)
order of initiliazers (-Wreorder)
just some palette depth stuff, nothing to see here
reduce copypasta
only look at SDL_Event.key for key-type events
make converted soldier zombies visible to begin with.
Merge pull request #883 from ajschult/keyUMR

only look at SDL_Event.key for key-type events
Merge pull request #882 from ajschult/warnings

Fix gcc compiler warnings from -Wall
Merge branch 'background_fps' of https://github.com/topaxi/OpenXcom

Conflicts:
	src/Engine/Options.inc.h
add item limit

configurable in craft rules, does not limit base defenses.
why you people want this is beyond me.
nope, don't like it, that's going off by default.