MEDIUM: htx: Change htx_sl to be a struct instead of an union

The HTX start-line is now a struct. It will be easier to extend, if needed. Same
info can be found, of course. In addition it is now possible to set flags on
it. It will be used to set some infos about the message.

Some macros and functions have been added in proto/htx.h to help accessing
different parts of the start-line.
5 files changed