Fixes walk aborting prematurely

when we still have enough TUs but destination is tile after closed ufo
door.
Add fps limiter for background window.
Background fps limit should not be 0 (possible div by 0).
only look at event button for button events
Option to enable 1:1.2 pixel aspect ratio
tooltips for inventory

because wtf do all those buttons mean anyway?
move bordered number text hack out of inventory and into numbertext
Two bugs in dogfight about chance to hit

1) Chance to hit a UFO should be adjusted according to UFO size, the
formula is CTH = (1+3/Size)/2*Accuracy, where Size is 5 for Very Small
to 1 for Very Large. This is how it was in original game, in OXC it is
just flat right now.

2) Projectiles try to impact again and again because missing does not
prevent a check for impact. Fixing this required changing the movement
code, because previously when projectile reached max range it would
immediately be considered to have missed, which would prevent
projectiles hitting at max range (for example, when cautious or standart
attack is chosen)
Merge remote-tracking branch 'upstream/master'
More languages
Don't let light sources blot out the sun.
give TU display a border for definition where applicable
syntax
Don't alter the "Days/Hours Left" display when selling items
whoops
Merge pull request #874 from IstrebiteI/dogfight_fix

Two bugs in dogfight about chance to hit
primed grenade indicators.
fix builder error question mark.

also an unused var that's been nagging me.
smooth out grenade flashing
colourize numbers and shift positions