Bug 5093: List http_port params that https_port/ftp_port lack (#1977)

To avoid documentation duplication, current https_port and ftp_port
directive descriptions reference http_port directive instead of
detailing their own supported parameters. For https_port, this solution
creates a false impression that the directive supports all http_port
options. Our ftp_port documentation is better but still leaves the
reader guessing which options are actually supported.

This change starts enumerating http_port configuration parameters that
ftp_port and https_port directives do _not_ support. Eventually, Squid
should reject configurations with unsupported listening port options.

src/cf.data.pre

@@ -2575,6 +2575,9 @@ DOC_START
 	The tls-cert= option is mandatory on HTTPS ports.
 
 	See http_port for a list of modes and options.
+	Not all http_port options are available for https_port.
+	Among the unavalable options:
+	- require-proxy-header
 DOC_END
 
 NAME: ftp_port
@@ -2639,6 +2642,9 @@ DOC_START
 
 	Other http_port modes and options that are not specific to HTTP and
 	HTTPS may also work.
+	Among the options that are not available for ftp_port:
+	- require-proxy-header
+	- ssl-bump
 DOC_END
 
 NAME: tcp_outgoing_tos tcp_outgoing_ds tcp_outgoing_dscp