Added ap_find_list_item() and ap_get_list_item() to util.c for parsing

an HTTP header field value to extract the next list item, taking into
account the possible presence of nested comments, quoted-pairs,
and quoted-strings. ap_get_list_item() also removes insignificant
whitespace and lowercases non-quoted tokens.

Work around a bug in Lynx regarding its sending "Negotiate: trans"
even though it doesn't understand TCN.

PR: 2065


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82775 13f79535-47bb-0310-9956-ffa450edef68