[Truffle] - A class definition raises TypeError if any constant qualifying the class is not a Module.
Too much entropy on my branch for now.

Revert "Update tests from MRI 2.1 branch."

This reverts commit 9c9187ced20deea0428d21b562760037d9d2c6e6.
More port-fixing for regsub and other stuff.

* More exact port of rb_reg_regsub
* Reverted fix to ASCGET logic that breaks a test; unknown reason
* Expanded strBufCat and related methods to take byte[].
More accurate (but maybe less efficient) encoded getc logic.