* Added TStringHash class

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26727 3ad0048d-3df7-0310-abae-a5850022a9f2
* Added AddReplacesExisting

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26728 3ad0048d-3df7-0310-abae-a5850022a9f2