- added checksum code for new format certificate. Will be enabled in v0.6, since it is not backward compatible
- fixed very stupid bug in radix64 cleaning function, causing any certificate to be accepted as a radix string
- added list of non backward compatible changes in README.txt, so that we can track them
git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@6030 b45a01b8-16f6-495d-af2f-9b41ad6348cc