Add some tests.
Add a comment. Kernel#require is defined in the mrbgem.
Add "test runner" support for cross builds.
 "test runner" means target simulator like QEmu, GDB sim, and so on. Also "test runner" might be debug agents for real targets.
If you do not setup test_runner, Rake will work same as before.
Add ARGV constant. It is not required by ISO. Compatibility with CRuby.
Change mruby-random License to MIT

refs: http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/license.html
Merge pull request #1160 from matsumoto-r/change_mruby_random_license

Change mruby-random License to MIT
Merge pull request #1150 from monaka/pr-add-test-runner-support

Add "test runner" support for cross builds.
Fix a memory leak in mirb
Merge pull request #1161 from h2so5/fix-memory-leak-in-mirb

Fix a memory leak in mirb
Merge pull request #1157 from monaka/pr-add-ARGV-to-mirb

Add ARGV constant. It is not required by ISO. Compatibility with CRuby.
Merge pull request #1144 from monaka/pr-add-iso-conformance-tests-20130406

Add more ISO conformance tests.