Handle non-native endian formats with SDL_sound
Fix a potential infinite loop.

If the first XDG_CONFIG_DIRS entry isn't a proper relative path,
it would never break the loop.
Check for MinGW in CMakeLists.txt instead of config.h
Add a configuration UI application

Not complete, but it's a decent start. Some problems:

* Only some otions are handled (backend-specific options in particular aren't
  handled).

* Does not warn when quitting with unsaved changes.

* Some options are missing tooltips.
Move alsoft-config to a separate project file

This to help avoid FindQt4.cmake from polluting the current project with
defines and include directories, applying them to targets that don't use Qt.
Require Qt 4.8 or newer for alsoft-config
Make sure QtCore and QtGui were found and link with the appropriate libs
Specify the required Qt4 version to find_package
Better specify include directories and defines needed for various targets
Use the COMPILE_DEFINITIONS property instead of DEFINE_SYMBOL
Properly check that Qt4 4.8+ was found