SSL-PROBLEMS: add "missing intermediate certificates" piece
README.http2: clarify the build prerequisites
RELEASE-NOTES: Synced with 8ddda0e999
openssl: info massage with SSL version used

Patch-by: byte_bucket
http2: free resources on disconnect

... and use Curl_safefree() instead of free()
TODO: remove http2, we now have it
chunked-encoding: provide a readable error string for chunked errors
ssh: abort immediately on a header callback error
ssh: removed a redundant close state transition
test640/1: add tests for --head with sftp and scp

This option is currently rather useless with these protocols
when no quote command is given, but it is valid.
docs: fixed a bunch of typos