Add comments.
Allow programmers to specify build path manually
Repalace int with mrb_bool because a return value is boolean.
Merge pull request #1385 from suzukaze/refactor-return

Repalace int with mrb_bool because a return value is boolean.
Fix warning by making call explicit
Merge pull request #1384 from xxuejie/customize-build-dir

Allow programmers to specify build path manually
Merge pull request #1388 from carsonmcdonald/toplevelwarnfix

Fix warning by making call explicit
Fix string test for so that it works for int16
Save mirb history when readline enabled
First round of trying to improve the performance of attr_reader and attr_writer. From ~24sec to ~15sec
Use env[USERPROFILE] for Windows
Changed use of MRB_INT_MAX to MRB_INT_MAX-1
Merge pull request #1391 from carsonmcdonald/fixfallbackarraysize

Changed use of MRB_INT_MAX to MRB_INT_MAX-1
Merge pull request #1389 from carsonmcdonald/stringtestfix

Fix string test for so that it works for int16
Merge pull request #1390 from kyab/mirb_history

Save mirb history when readline enabled
Merge pull request #1382 from suzukaze/add-comments

Add comments in irep.h
rename advance_phase to incremental_gc_until

in fact advance_phace() is not really a "phase", but can be used
as an utility function.
cleanup redundant codes with incremental_gc_until()
Wrote tests around attr, attr_reader, attr_writer, attr_accessor
Merge branch 'master' into attr-perf-fix

Conflicts:
	mrblib/class.rb