CSSMin: Support parenthesis and quotes in url references

CSSMin: Support parenthesis and quotes in url references

Previously they were often being cut short due to the url pattern
ending at the first single quote, double quote or closing parenthesis
regardless of which of those started the url match.

Running benchmarkCSSMin.php before and after the change doesn't seem
produce consistent improvement or regression. Repeated runs with count=100
with and without this change both have a median between 2.6ms and 2.9ms
using PHP 5.6, and between 2.6ms and 2.8ms using HHVM 3.12.

Bug: T60473
Change-Id: I6d6a077ad76588f3ed81b1901a26b7e56d2157ee