mruby should be throw a NameError, if class variable is not exist.
Added MRUBY_LIBS to mrbgems Makefile
Support MakefileGemList for MRUBY_CFLAGS and MRUBY_LDFLAGS

Other apps using mruby like mod_mruby easy to link mrbgems dynamically by MakefileGemList
Merge pull request #666 from skandhas/pr-add-nameerror-for-mrb_mod_cv_get

mruby should be throw a NameError, if class variable is not exist.
Merge pull request #667 from masuidrive/add_mruby_libs_to_makefile

Added MRUBY_LIBS to mrbgems Makefile
Merge pull request #668 from matsumoto-r/support_gem_flags_list

Support MakefileGemList for MRUBY_CFLAGS and MRUBY_LDFLAGS
add mrb_mod_cv_defined and mrb_cv_defined
add mrb_mod_cvar_defined
add test for Module#class_variable_defined?
Merge pull request #669 from skandhas/pr-add-Module-class-variable-defined

Add Module#class_variable_defined? for mruby
Support GEM_LIBS_LIST in Makefile4gem
Merge pull request #670 from matsumoto-r/support_gem_libs_list

Support GEM_LIBS_LIST in Makefile4gem
add mrb_mod_remove_cvar
add test for Module#remove_class_variable
Merge pull request #671 from skandhas/pr-add-Module_remove_class_variable

Add Module#remove_class_variable for mruby.
replace all slash to backslash in `cd /path/to/folder` for windows.
Merge pull request #672 from mattn/cd_backslash

replace all slash to backslash in `cd /path/to/folder` for windows.
use readline if it's enabled.
Merge pull request #674 from mattn/readline

use readline if it's enabled.
wrong stack position for headless case; close #675