instead or additionally to string.h, in preparation for functions move.
* moves str[n]casecmp() functions and others to strings.h.
* strings.h doesn't include string.h anymore.
* this solves #10949
bug #1875.
* This does not apply when retrieving the string from stdin, though.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24176 a95241bf-73f2-0310-859d-f6bbb57e9c96