Fix Range#==
Fix some signed unsigned warnings, int to size_t.
Change int to size_t.
Change int to size_t
Merge pull request #1322 from suzukaze/refactor-range-c

Refactor range_eql() func in rangec.c and add Range#eql? method test.
Merge pull request #1324 from h2so5/fix-range-equal

Fix Range#==
Merge pull request #1325 from carsonmcdonald/unsignedfixes

Fix a few unsigned signed comparison warnings
Add mrb_class_get_under()
Merge pull request #1327 from h2so5/add-mrb_class_get_under

Add mrb_class_get_under()
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.