prot: add prot_puts()

(this is cherry-picked from caldav-2.4, but just the prot changes)
berkdb: support version 5.0->5.3

Cherry picked from caldav-2.4.
Added support for channel bindings (patch by Luke Howard)
Added GS2 plugin from Luke Howard
Only enable GS2 plugin if gss_inquire_mech_for_saslname is defined in gssapi.h
Fixed one spelling error copied all over the file
Merge from Luke Howard: Use draft-josefsson-gss-capsulate-01 if present.
Added GSS-SPNEGO plugin which can also be used for HTTP Negotiate auth (RFC 4559)
mailbox: make uidvalidity stick and bump modseq on rename
prot_printf: unsigned fix
prot_printf: %x %lx %llx support
prot: prot_vprintf
tls.c: add servername_callback to log servernames sent by clients
tls.c: only use servername_callback on version 1.0.0+
tls.c: only use servername_callback on version 0.9.8f+
tls.c: make note about client-side context for iSchedule