Fix exit

Improve recent CRuby rake compatibility

Add syntax error for incomplete global variables

Add syntax error for incomplete instance/class variables

Support NameError#name

Add `NameError#name`. Fix `NameError.new` and `NameError.initialize`. Enable 2nd argument for `NameError.new` in C API.

Change to return the exception object when an exception occurred in mrb_funcall

Adjust ci->nregs to prevent heap corruption

Add ISO confomance tests

Check malloc failed

bugfix: Kernel#!=, and add #!= testcase.

Cleanup around mrb_raise calls

Add fib39.rb to benchmark/