Some improvements to the GP editor:
    - GP are now classified into groups, just like tracks: standard, user defined, and add-ons
    - allow empty GPs to be loaded by the GP manager, so that they can appear
      on the GP editor (but not on the track selection screen)
    - enable/disable buttons depending on the available options
    - provide some feedback after pushing the "save" button
    - some minor bug corrections and improvements
Turn sfx_manager into a singleton.
Removed old/unused declaration.
Move m_sync
Removed unnecessary static variable.
Added comments.
commenting out an unused function which only throws deprecation warnings
Queue up sfx instead of starting them immediately. Preparation for
threading the sfx manager.
Merge branch 'master' of github.com:supertuxkart/stk-code
Fixed incorrect value for opengl version.
Report available RAM on linux.
Started to add GL limits to the statistics. Work in progress.
Fixed (c) statement.
Report memory on windows and osx (not tested).
Added a version number to the hardware report, and report the hw config
only once per installation. Print error messages in case submitting the
request.
Don't submit requests for now (server is still expecting compressed
data, and can't handle he requests we send atm).
Fixed various compiler warnings.
Removed unused code and objects.
Made the user_id (which is apparently necessary on the server to calculate
number of configurations correctly) a random number, that is saved in the
config file.
Made line endings consistent.