Merge pull request #2160 from nobu/space

Space
use Kernel#__send__ insteard of Kernel#send
Implement Struct#to_h .
Added dump_irep in header.
Merge pull request #2162 from ksss/__send__

use Kernel#__send__ insteard of Kernel#send
Merge pull request #2163 from take-cheeze/struct_to_h

Implement Struct#to_h .
Implement header search for gcc and clang.
Use header searcher to find readline and linenoise.
Merge pull request #2164 from scalone/public_dump_irep

Added dump_irep in header.
Merge pull request #2165 from take-cheeze/header_searcher

Implement header searcher to use readline in mirb if possible.
Remove use of define_singleton_method.
On overflow, clear new stack space before mrb_raise
Merge pull request #2166 from take-cheeze/fix_for_1_8

Remove use of define_singleton_method.
Merge pull request #2168 from carsonmcdonald/stackclearfix

On overflow, clear new stack space before mrb_raise
goto STOP if ridx==0
Merge pull request #2169 from takeru/load_crash

goto STOP if ridx==0
Implement Struct#values_at and Array#values_at .
Add API `mrb_get_values_at()` to mruby/range.h .
Update time.c

miss __MINGW32__ macro check
Merge pull request #2170 from windwiny/patch-1

Update time.c
Refactor rshift