sshbuf_fixed: the parent buf is not mutable
ssh-keygen: missing s/sshbuf_get_stringb/sshbuf_froms/
packet.c: convert to sshbuf_froms()
mux.c: replace sshbuf_get_stringb with sshbuf_froms
replace sshbuf_new/sshbuf_put with sshbuf_from.
remove remaining PACKET_SKIP_COMPAT* defines
ssh_api: add copyright
replace Kex typedef with 'struct kex'
replace Newkeys typedef with 'struct newkeys'
replace Mac typedef with 'struct sshmac'
replace Enc typedef with 'struct sshenc'
replace Comp typedef with 'struct sshcomp'
ssh->current_keys is redundant, replace with ssh->kex->newkeys
packet.h: replace include of kex.h with forward declaration
authfd.c and mac.c do not need kex.h
packet.h: replace include of key.h with forward declaration
replace Cipher typedef with 'struct sshcipher'
replace CipherContext typedef with 'struct sshcipher_ctx'
packet.h: remove include of cipher.h
mm_newkeys_to/from_blob no longer exist