Turns out I mistook @celticminstrel's opinion that we should use include guards over pragma (737916e).
Since all major compilers support `#pragma once`, there's no reason not to use it.
For future mergability reasons, this excludes src/spirit_po and src/xBRZ. It also excludes src/boost-patched.
This commit converts the following function calls:
* boost::bind -> std::bind
* boost::function and boost::functionN -> std::function
* boost::ref and boost::cref -> std::ref and std::cref
* boost::bad_function_call -> std::bad_function_call
In the process, it was discovered that std::bind has trouble with overloaded
functions. There were two such cases in the code:
* gui2::twindow had an ancient unused overload to draw(). The overload was removed.
* gui2::trepeating_button was binding tdispatcher::fire. This case was converted
to a lambda.
previously it showed the default "do you want to quit the game" message
when leaving the editor. using the red cross in the corner.
This also changes some dublication of the "Do you really want to quit?"
translatable string in the c++ code.
when quitting (for example by clicking on the red cross in the corner) the
game now asks for a confirmation, if there is currently a (re-)play or
the editor running.
