Remove escaping for @external names.

fixes #106
Merge pull request #107 from dankurka/remove_external_escaping

Remove escaping for @external names.
Merge branch 'master' of github.com:jDramaix/gss.gwt into jd_issue_86

Conflicts:
	src/test/java/com/google/gwt/resources/converter/Css2GssTest.java