Remove some deprecated global functions

Some uses remained in Gerrit extensions, and patches have been submitted
to replace the usages. See below for details.

* in_string (deprecated in 1.21)
* wfGenerateToken (deprecated in 1.20) (had 2 uses)
* wfStreamFile (deprecated in 1.19) (had 1 use)
* wfUILang (deprecated in 1.18)

Change-Id: Ic67a968da8f37daf44503b98d00710eb99180805