tx and rx filtering, up and down conversion, now for frame sync

git-svn-id: https://svn.code.sf.net/p/freetel/code/codec2-dev@1892 01035d8c-6547-0410-b346-abe4f91aad63
first pass at coarse timing (frame sync), syncs up OK

git-svn-id: https://svn.code.sf.net/p/freetel/code/codec2-dev@1893 01035d8c-6547-0410-b346-abe4f91aad63