Add syntax error for incomplete global variables
Improve CRuby rake compatible
Fix exit
Merge pull request #1138 from h2so5/syntax-error-for-incomplete-global-variable

Add syntax error for incomplete global variables
Merge pull request #1139 from masuidrive/build

Improve recent CRuby rake compatibility
Merge pull request #1141 from mattn/fix_exit

Fix exit
use EXIT_SUCCESS and EXIT_FAILURE for exit status; close #1142
parse_args should return either EXIT_SUCCESS or EXIT_FAILURE
comment E_* macros to address concerns in #1143