Add XRegExp from https://github.com/slevithan/xregexp/tree/d06eff50f87d81d2dd3afc1e854784c38b17bcc4/src
Load XRegExp into Zotero.XRegExp and Zotero.Utilities.XRegExp and make it accessible from translators.
Remove unnecessary character classes. Add some useful ones.
Eliminate race condition during processDocuments call with multiple URLs
Merge pull request #226 from aurimasv/processDocuments

Eliminate race condition during processDocuments call with multiple URLs
Properly handle cases where no translator is specified
Don't report web translator errors if there is a parent translator
Merge pull request #227 from aurimasv/complete

Complete
Fix sync error (since beaaf8fc)
Use 100 lines
Merge remote-tracking branch 'aurimasv/xregexp' into 3.0
Tweak loading process
Merge branch '3.0'

Conflicts:
	chrome/content/zotero/recognizePDF.js
	chrome/content/zotero/xpcom/utilities.js