cmake/wxWidgets: fix debug builds on Linux
desura/lin: clean up bootloader and don't fork before execution

fixes #585

this forking lead to some missbehave in gdb, also it doesn't make much sense.

I also cleaned some unused methods and simple single line function away, so that this class should be more straight forward.

v2: fix compile error on non DEBUG builds
Merge pull request #600 from karolherbst/bug585

clean up bootloader and don't fork before execution also wxgtk debug build fix
version: note #585 fix in changelog