Multilocale chdir testing

Add two tests of the chdir()/cwd() functionality.  The first test locks in the
behavior in a multilocale context; chdir() calls on one locale will not
affect cwd() calls on a different locale.  The second test indicates
behavior in a single locale/multiple tasks environment; chdir() calls
from one task will affect cwd() calls in a different task on the same
locale.

This behavior is now indicated in the comments for these functions.