Add Object#instance_exec
Fix unsigned/signed comparison.
Fix unsigned/signed warning.
Fix signed/unsigned warning.
Refactor mrb_realloc() func in gc.c.
Add Range#eql? test case.
Refactor mrb_ary_equal() func in array.c.
Refactor mrb_ary_eql() func in array.c.
Merge pull request #1329 from carsonmcdonald/unsignedsignedfix2

Unsigned signed warning fixes
Merge pull request #1330 from suzukaze/refactor-gc-c

Refactor mrb_realloc() func in gc.c.
Merge pull request #1331 from suzukaze/add-range-test

Add Range#eql? test case.
Merge pull request #1332 from suzukaze/refactor-array-c

Refactor mrb_ary_equal() func and mrb_ary_eql() func in array.c.
Merge pull request #1328 from h2so5/add-object-instance-exec

Add Object#instance_exec
Refactor mrb_define_class() method in class.c.c
Merge pull request #1334 from suzukaze/refactor-class-c

Refactor mrb_define_class() method in class.c.c