Some basic string tests.

I wrote up some basic string tests, just to get a feel.  You can find 
them at:

http://jryan.perlmonk.org/images/stringtest.tar.gz

Things of note:

-I wasn't sure how the tests should be written, so I wrote them in a generic
'code in .t, expected output in .o' form.  This should be pretty easy to
convert to whatever is decided.

-Things that are currently unimplemented in P6C are in the TODO folder, per
David Wheeler's suggestion.

-I added the original P6C string test that I wrote to the tarball for
comparison; its 'p6corig.t'.  This uses a system that P6C uses;
it is built off of Parrot's Parrot::Test, which is built off of
Test::More.