check sanity for cdk headers, on arch and other places
autoreconf
Clarify what lower security levels mean (Issue #40).
Helpful messages for adding keys (Issue #40).

- add ^K to the statusline
- make it obvious that ^A adds a key
Nicer messages for unknown key validity (Issue #27)
Re-fix CDK tst for debian and other systems with old CDK.
CDK 20060507 from debian works, as always.
bump version to 0.31
autoreconf and encryption-result
put README where people can see it
Wide range of explanations for signature summary errors (Issue #27).
Merge tag '0.31' into debian
Imported upstream release 0.31