Fixed a few "strip tag exposed" bugs.

Fixed a few "strip tag exposed" bugs.
* Introduced Parser::killMarkers() based on the concept from StringFunctions. Used it in cases where markerStripCallback() doesn't make sense semantically, namely grammar, padleft, padright and anchorencode. Used markerStripCallback() in other cases.
* Changed headline unstrip order as suggested by P.Copp on bug 18295
* In CPF::lc() and CPF::uc(), removed the is_callable(). This was a temporary testing hack committed by me in r30109, which allowed me to do differential testing against a copy of the parser from before that revision.