(chunga:read-http-headers stream &optional log-stream)
|Function: Reads HTTP header lines from STREAM (except for the initial status line which is supposed to be read already) and returns a corresponding alist of names and values where the names are keywords and the values are strings. Multiple lines with the same name are combined into one value, the individual values separated by commas. Header lines which are spread across multiple lines are recognized and treated correctly. Additonally logs the header lines to LOG-STREAM if it is not NIL.