Eliminate redundant CHR() macros.

See http://docs.wxwidgets.org/trunk/classwx_string.html#string_vararg
for explanation about how it is not needed for wxFunctions like
String::Format or wxLogMessage.

Also changed CHR's C-style cast to a safer static_cast.
Merge branch 'master' of https://github.com/sirjuddington/SLADE
Thing path stuff reworked a bit.

Fixed an operator precedence bug.
KDIZD titlemap looks correct again.
Dragon paths are back.
Merge pull request #73 from Gaerzi/master

Sync with my fork.