Compatibility fixes

Some fixes to update test compatibility:
- Got rid of ```#r2only``` for R3-supported alternate literal forms.
- Added ```#r3only``` test for ```#``` none literal.
- Fake closures are in R2 proper since 2.7.7, no tag needed.
- Made closure mold test ```#r3only```.
- Added missing ```#r3only``` datatypes.
- Added fake R2/Forward datatypes as ```#r3```.
- Split out bug#1477 from bug#1432.
- Changed ```#r3only``` to ```#r3``` for successfully faked ```map!``` stuff.
- Added ```#r3``` tests for sucessfully faked ```typeset!``` stuff.
- Changed ```none``` passthrough tests from ```#r3``` to ```#r3only```.
- Made bug#1711 test less ambiguous.
- Made ```file-type?``` test ```#r3only``` - it's not planned to backport.

Even though the fake datatype stuff has been included in R2 2.7.7+
it doesn't work well enough to merit testing for it in R2, so those
are ```#r3``` tagged. The closure stuff works great though, so the tags
are off for those tests where applicable.

The none passthrough stuff affects natives, so it's against policy
to change those in R2/Forward. Codecs aren't planned either, so
no ```file-type?``` function.