Rebuild CRuby based building script without Makefile

Tested CRuby 1.8.6 and 1.9.3

You can see building configuration in build_config.rb
Merge pull request #679 from masuidrive/merge_to_cruby_building_script

Rebuild CRuby based building script without Makefile
Merge branch 'master' into mrbgems

Conflicts:
	Rakefile
	mrbgems/GEMS.active
	mrbgems/build_tasks.rb
	mrblib/Makefile
	src/Makefile
Adapter mrbgems documentation to rake system
Merge pull request #680 from bovi/doc-rake

Adapter mrbgems documentation to rake system
build config update of mrblib/ext
add '-I#{MRUBY_ROOT}/src'
Fix documentation for mrbgems
Merge pull request #682 from bovi/doc-rake

Fix documentation for mrbgems
add src/ext/mruby_ext.rake
remove mrbgems/g/process
update build configuration
build task bug fixes
test driver update (support MTest::Unit)
Merge branch 'master' into iij