Author: Tim Hunt
MDL-20636 Fix a bunch of minor errors in the truefalse preview.
Most significantly, all behaviours now work.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=cce1b6556cb380b8bb295a4568421e1a3cd645d5
http://github.com/moodle/moodle/commit/cce1b6556cb380b8bb295a4568421e1a3cd645d5
+ 2.1dev en [hexanotallowed,qtype_calculated]