MINOR: h2: clarify the rules for how to convert an H2 request to HTX

The H2 request parsing is not trivial given that we have multiple
possible syntaxes. Mainly we can have :authority or not, and when
a CONNECT method is seen, :scheme and :path are missing. This mostly
updates the functions' comments and header index assignments to make
them less confusing. Functionally there is no change.
1 file changed