Fixed up various command line option scenarios:

Fixed up various command line option scenarios:
  - If no tool is specified, V now gives a short message and a list of
    available tools.  This was meant to happen previously, but a bug prevented
    it from working properly;  it gave the usage message instead.

  - If a bad option is given, V now gives a short message rather than the full
    --help.  This make V consistent with all other programs I looked at.

  - Now returning 0 when you do 'valgrind --help' and 'valgrind --version'
    as other programs do.

  - Removed VG_(startup_logging)() and VG_(shutdown_logging)() as they were
    empty and have been for a long time (always?).

  - Added various tests for these scenarios.  Had to change the regtest
    script slightly to allow for malformed command lines.

This addresses bug (wishlist) #82999.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2418