works just about exactly like the amiga.lib RVI code used to do, which means
that there is no artificial length limit for the number of characters a string
retrieved may have, and the code is largely reentrant.
git-svn-id: file:///Users/olsen/Code/migration-svn-zu-git/logical-line-staging/clib2/trunk@15191 87f5fb63-7c3d-0410-a384-fd976d0f7a62