Separate translation units avoids compiler generated CRC tables being
linked when not needed.
Also only compile once and add to wsjt_cxx library for later link
editing.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7631 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
Bill Somerville