~samwhited/xmpp

ref: d4b835bf2b08a22e6a13cd9b33e62c88f9854677 xmpp/internal/decl d---------
all: add missing canonical import comments

Signed-off-by: Sam Whited <sam@samwhited.com>
internal/stream: new package for stream parsing

Also update all uses of old internal identifiers that were moved into
internal/stream.
internal/decl: new XML declaration package