Add API `mrb_atexit()`.
`mrb_final_mrbgems` will be called as mrb_state atexit function.
Maybe useful in #1844.
Change to use assert method.
Remove space.
Merge pull request #2334 from yui-knk/remove-space

Remove space.
Fix typos in gc
Merge pull request #2336 from katmutua/master

Fix typos in gc
remove part of 9cd71916 test for same reason as 5306e47
Merge branch 'master' of github.com:mruby/mruby
Remove space.
Fix indent.
Merge pull request #2342 from yui-knk/fix-indent

Fix indent.
Merge pull request #2341 from yui-knk/remove-space

Remove space.
Fix mgem test args passing
Change to always use locals->car->car.

When p->locals->car is not NULL and p->locals->car->car is NULL,
local_add_f dose not append sym to p->locals->car->car.
This commit change to append sym to p->locals->car->car.
This will close #2333.
Merge pull request #2343 from carsonmcdonald/fixmgemargspassing

Fix mgem test args passing
Add comments in String#lstrip, rstrip, strip, lstring_bang, rstrip_bang and strip_bang
Fix indent in String#casecmp comments
Implement `NoMethodError#args`.
Add Array#to_h
Merge pull request #2345 from suzukaze/add-string-comment

Add comments in String#lstrip, rstrip, strip, lstring_bang, rstrip_bang ...