Fixed the quantifier that optionally matches a quote before the
filename. This was originally reported in the homebrew project[1].
Note that this fix is different than patch posted there, as there are
some platforms that don't have the quote, so it needs to be included
in the expression optionally.

[1]: https://github.com/mxcl/homebrew/issues/12567#issuecomment-6434000

Change-Id: Ibf2ed93ce169d80932e877f942dc4eeb03867f8b