Add fpwidestring unit

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29145 3ad0048d-3df7-0310-abae-a5850022a9f2
 Add fpwidestring unit

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29146 3ad0048d-3df7-0310-abae-a5850022a9f2