Add comments.
Fix string test for so that it works for int16
Save mirb history when readline enabled
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()
Improve Android NDK toolchain support.

Linux-x86_64 has not been supported now.
This commit add Linux-x86_64 platform support.
Fail if dependency isn't found
Merge branch 'master' into attr-perf-fix
Reset the so-render benchmark so that it is what it was before my attr performance testing.
Cleaned up some of the Module#attr tests
Merge pull request #1393 from crimsonwoods/add-android-ndk-linux-x86_64-support

Improve Android NDK toolchain support.
Merge pull request #1395 from carsonmcdonald/fixdepcheck

Fail if dependency isn't found
Merge pull request #1396 from Archytaus/attr-perf-fix

Performance improvement of methods generated by Module#attr
change else formatting