Don't zero dd() when data come from disk.
Some code cleanup.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/map65@2470 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
MAP65 v2.3.0, r631, as checked out from the SVN repository on
pulsar.princeton.edu. If all goes well with this commit, subsequent
MAP65 development will use the Berlios repository.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/map65@2461 ab8295b8-cf94-4d9e-aec4-7959e3be5d79