class/module body to honor whether value is required or not; reduce a few instructions for normal cases
fix #1617
Change :vattr= to :cattr= in respond_to? test
rename mrb_intern_litral -> mrb_intern_static
zero copy intern from static allocate irep
zero copy str_new from static allocate irep
clear STR_NOFREE flag on modify
avoid copying when the original string comes with MRB_STR_NOFREE
wrong operator precedence fixed
use static symbols for debug filename info
Add more testing for singletons
Fix return when value expected
revert fix in #1620
adjust register position for return value; fix #1620