[mod_ajp13] fix crash with bad response headers (fixes #3170)
[mod_ajp13] fix crash with bad response headers (fixes #3170)

fix crash with bad response headers from AJP13 backend

(thx Michał Dardas)

x-ref:
  "mod_ajp13 read heap buffer overflow"
  https://redmine.lighttpd.net/issues/3170

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