MINOR: mux-h1: Split front/back h1 stream creation in 2 functions

Dedicated functions are now used to create frontend and backend H1
streams. h1c_frt_stream_new() is now used to create frontend H1 streams and
h1c_bck_stream_new() to create backend ones. Both rely on h1s_new() function
to allocate the stream itself. It is a bit easier to add specific processing
depending we are on the frontend or the backend side.
1 file changed