Did some profiling, conclusions:
 - we want to buffer our input streams, apperantly wx doesn't do this automatically
 - compiling regexes is SLOW.
   This is not just in the numbers, but it is actually noticable! The textbox used to be quite unresponsive.
   I wrapped the call to filter_text in the game file with a quick contains() call, so usually, the regex doesn't fire.
   It would be nicer if this was somehow automatic, but that will not be easy.