add some tests for case statements
Merge pull request #1613 from h2so5/test-case-statements

add some tests for case statements
change behavior of mrb_sym2str
Remove 'mrb_state' field from 'kh_xxx_t' structure.

'kh_xxx_t' requires 'mrb_state' to allocate, free, and compute hash value.
But 'mrb_state' should not be held by 'kh_xxx_t' and 'mrb_state' should be
supplied from outside.
Merge pull request #1614 from h2so5/change-sym2str

change behavior of mrb_sym2str
Merge pull request #1615 from crimsonwoods/remove_strong_coupling_by_khash

Remove 'mrb_state' field from 'kh_xxx_t' structure.
verify the argument of String#=~
Merge pull request #1616 from h2so5/verify-string-match

verify the argument of String#=~
string type check based on #to_str to encourage duck typing; #1616
remove MRB_IREP_ARRAY_INIT_SIZE which is no longer used
zero copy C literal strings in symbol table
Merge branch 'master' into iij

Conflicts:
	test/t/syntax.rb
fix #1617
Merge pull request #1618 from h2so5/fix-1617

fix #1617
Merge branch 'master' into iij