Change version labels to work better with GIT

Change version labels to work better with GIT

 - The guess-rev.sh script is now a tweaked version of "setlocalversion" as
   seen in Linux, U-Boot, and various other projects.  When it finds source
   control support (git, hg, svn) it uses IDs from there.  Else (specific
   to this project) it reports itself as "-snapshot", e.g. from gitweb.

   I verified this new "guess-rev.sh" script runs under Cygwin.

 - Also update the generic version strings to be like "0.3.0-dev" (during
   development) instead of the very long "0.3.0-in-development".  These also
   show up in the PDF docs.  For better tracking, we might eventually change
   these strings to include the version IDs too.

 - Change the startup banner version strings so they include the guess-rev
   output.  Development and release versions with GIT will be like

    Open On-Chip Debugger 0.3.0-dev-00282-g7191a4f-dirty (2009-10-05-20:57)
    Open On-Chip Debugger 0.3.0 (2009-10-05-20:57)

   instead of the previous SVN-specific (even when using git-svn!)

    Open On-Chip Debugger 0.3.0-in-development (2009-10-05-01:39) svn:exported
    Open On-Chip Debugger 0.3.0 (2009-10-05-01:39) Release

git-svn-id: svn://svn.berlios.de/openocd/trunk@2809 b42882b7-edfa-0310-969c-e2dbd0fdcd60