Merge pull request #984 from monaka/pr-make-mrb_str_new2-obsolete

Remove mrb_str_new2().
Merge pull request #985 from monaka/pr-remove-unused-code-20130312

Remove mrb_str_sublen() as it is not used.
Merge pull request #986 from monaka/pr-use-mrb_obj_alloc_string-instead-of-str_alloc

Remove str_alloc(). Use mrb_obj_alloc_string() instead.
mrb_sys_fail raises SystemCallError if we have it.
Merge branch 'master' into pr-systemcallerror
Merge branch 'master' into pr-systemcallerror
mrb_str_new2 -> mrb_str_new_cstr
set DATA_TYPE as soon as possible.
Add the type check in mrb_str_to_cstr().
Simplify. Temporary variable "i" is removed.
Extract stack zero filling to stack_clear(). Porting evelopers can optimize by replacing to memset() on their own risk.
Add null check
Cut off eval_test from main
Merge pull request #1003 from kano4/pr-add-null-check

Add null check
Merge pull request #1004 from kano4/pr-cut-off-eval_test

Cut off eval_test from main
Merge pull request #996 from iij/pr-systemcallerror

mrb_sys_fail raises an instance of (subclass of) SystemCallError if we have it
Merge pull request #1000 from iij/pr-set-data-type-asap

DATA_TYPE must be set as soon as possible
Merge pull request #1002 from monaka/pr-extract-stack-zero-filling

Extract stack zero filling into new function.
Merge pull request #1001 from monaka/pr-add-type-check-in-mrb_str_to_cstr

Add the type check in mrb_str_to_cstr().
Remove compiler warning