Change tracking:

Change tracking:

 * rename output_changes to outputChanges
 * rename tracking_changes to trackChanges
 * add FIXMEs for later revision
 * remove trackChanges(); the CT data structure will always be set up
 * decouple LFUNs changes-output/change-accept/change-reject/
   all-changes-accept/all-changes-reject from LFUN changes-track

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15261 a592a061-630c-0410-9148-cb99ea01b6c8