Mark `ParseError` as a PHP7 builtin class
Mark `ParseError` as a PHP7 builtin class

Summary:
Ref T12855. In D18797, I introduced a `catch (ParseError ...)` to deal with a PHP7 special case. However, this class won't exist in earlier versions of PHP like PHP5.

@lpriestley reports hitting an error with this under PHP5 ("unknown class/interface ParseError") from the linter while running `arc diff`, which is expected since I didn't add it to the secret list of special PHP7 magic.

Add it to the PHP7 magic.

(It's fine that we catch something which may not exist in PHP5, since `Throwable` does not exist in PHP5 and the `catch (Exception ...)` above will catch everything which can be caught in PHP5.)

Test Plan: Will make @lpriestley try again.

Reviewers: amckinley, lpriestley

Reviewed By: amckinley

Subscribers: lpriestley

Maniphest Tasks: T12855

Differential Revision: https://secure.phabricator.com/D18809

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