For /showgroup output, reduce the per-message length by one character to leave space for the trailing nul.
For /showgroup output, reduce the per-message length by one character to leave space for the trailing nul.

git-svn-id: c0942edff5350604e2827ab28bdfcfa5200fadee@20791 08b3d480-bf2c-0410-a26f-811ee3361c24

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