New fstest to check rename POSIX conformance

This patch is a newer version of the test presented on

http://www.rtems.org/pipermail/rtems-devel/2014-February/005318.html

Unchecked error cases:

- EIO (physical error)

- ENOSPC (no space left in the new filepath)

- EROFS (already covered on testsuites/fstests/fsrofs01)

Untested functionality:

- File system lock during rename() operation

- If after rename() the link count of a file becomes 0 it should be
removed and the space ocupied by the file shall be freed and no longer
accessible (the function statvfs() gives "not implemented" on the imfs
file system, so this is postponed for now)