set defaults for revisions, rewind and ARM tabs of the prefs window (in
addition to the CRT tab). set defaults button labelled appropriately
fixes some race conditions caused by pre/post hooks on prefs values -
prefs values are generally goroutine safe, except when pre/post hook is
defined
pref types are likely to be called in critical sections. to make the
prefs package easy to use, values in the types were protected by
mutexes, this is relatively expensive however. with the exception of the
generic type, critical sections are now protected with atomics.
small performance improvement
the note about historical versions also being covered wasn't strictly
needed and was ugly. the LICENCE being in the root file from the very
first commit is sufficient.
amended debugger and existing preference values to use prefs package
amended sdlimgui to store window size/position using the prefs package
amended hiscore mechanism to use prefs package to store server & authentication
