REORG: mux-fcgi: Extract flags and enums into mux_fcgi-t.h

The same was performed for the H2 and H1 multiplexers. FCGI connection and
stream flags are moved in a dedicated header file. It will be mainly used to
be able to decode mux-fcgi flags from the flags utility.

In this patch, we move the flags and enums to mux_fcgi-t.h, as well as the
two state decoding inline functions.
2 files changed