Port to Psyntax-mosh

[okuoku]

Since the original Mosh now implementing R7RS, we should be able to port Yuni to it.

[okuoku]

Psyntax do not support "expand-to-library" styled macros. Filed higepon/mosh#199

Mosh compiler has define-macro so there's some chance we can implement Yuni on it instead, without hygienic macros, just like s7 or Gambit.