Fix handling module beginning with v and pragma with version.

[yak1ex]

The following 2 issues are fixed by this pull request. Both are related with using version pragma.

• module beginning with v
• pragma with version requirement

Please note that t/20_parse_self.t is also adjusted because version is ignored in the test.

Details are as follows:

• module beginning with v
  • Issue: For example, for the case of use version, just a letter 'v' is matched to the rule <version> and the rest, 'ersion' is left. The rule <use_stuff> is matched because the rule <version> is matched but the regex /[;}]/ in the rule <token_use> is not matched to 'ersion'. Thus, the rule <token_use> fails to match completely (don't backtrack).
  • Fix: Adjust regexp of <version> not to match to words like 'version'.
• pragma with version requirement
  • Issue: Even after the above fix, use version 0.77 can not be detected. Trying to match to the rule <pragma>, the rule <import_list> is matched to just a letter '0' then <token_use> fails the way similar to above.
  • Fix: Remove the rule <pragma> to fall back to the rule <module>. I think this is fair because a pragma is just a module.

[charsbar]

Thanks and sorry for the delay.