[mod_extforward] support longer PROXY v2 TLV vec
[mod_extforward] support longer PROXY v2 TLV vec

support longer HAProxy PROXY protocol v2 TLV vector
(allow up to 2k total for header + TLVs, saved on stack,
 and expecting <= MTU size (typically 1536 bytes))

lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4