Fix the problem discussed in

Fix the problem discussed in

Subject: [ID 20001015.004] Fwd: Tie::SubstrHash -- bug & fix (all Perl versions)
Date: Mon, 16 Oct 2000 04:48:59 +0300 (EET DST)
Message-Id: <200010160148.EAA14523@alpha.hut.fi>

originally from Linc Madison.  Also Andreas König's comments
taken into account.  Some other problems with Tie::SubstrHash
fixed: didn't croak when the table exceeded the requested number
of entries (as documented) but instead when the number of entries
exceeded the size of the table, a croak() had an unnecessary \n,
didn't have a CLEAR method, documented that there is no exists().
Didn't fix to be strict-proof because the module uses &foo; and
dynamic scope.  Added a test script exercizing both first tamely
the basic functionality, and then the failure cases reported by
Linc Madison.

p4raw-id: //depot/perl@7530