clean up image loading a bit. gets rid of useless "Passed NULL data source" or PhysFS file not found errors

committing patch from issue #798, as requested by unC0Rr

fix cabal build (on linux)

fix for "Unexpected semi-colons in conditional" issue, as reported by YuGiOhJCJ (see http://www.hedgewars.org/node/5860 ) big thanks to burp for helping to identify and fix this issue

Some further work on map optimizer

tweak untint a little (especially in connection with GrayScale)

theme configurable sudden death music. untested

allow teleporting outside Land[]

escape info message arguments, fixes issue #801: Frontend parses INFO command output as html

collision indicator on failed girder placement (especially useful with rubberband I guess). still needs some tweaks but I am going to bed now :P