Simplify version parsing for `ArcanistPhpLinter`
Simplify version parsing for `ArcanistPhpLinter`

Summary: We can use `php --run "echo phpversion();"` to return a nice, compact representation of the PHP version.

Test Plan: `arc unit`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11264

julkiewicz/arcanist,julkiewicz/arcanist,julkiewicz/arcanist,julkiewicz/arcanist