First attempt at caching tangents meshes
Second try of my previous pull request, which was partially reverted due to caused crashes and memory leaks
Merge remote-tracking branch 'upstream/master'
This will (hopefully) solve the memory leaks in dynamic ribbons and image button widgets
Issue #1588

Fixed crashes in track info screen
Fix #1170 Add "Don't Assign" option when configuring inputs
Check texture cache before adding an icon button's disabled texture
Fix #1153 Cleanup logging code
Fixed compiler warning.
Avoid writing the players.xml file multiple time at the exit time.
Use CMAKE_CXX_FLAGS instead of add_definitions for additional flags
Merge branch 'master' of https://github.com/supertuxkart/stk-code
Fix loss of associated online user name if stk is played offline
(might be a fix for #1595).
Merge branch 'master' of github.com:supertuxkart/stk-code
Fixed compiler warnings
Merge branch 'master' of https://github.com/supertuxkart/stk-code
Merge pull request #1606 from Flakebi/fix

Fix some more bugs
Fixed missing quotes
Added secret achievement (i.e. progress not shown in list).
Actually display secret achievements once they have been achieved.