Clean up an edge case where obs-fold continuation preceeds the first header,

as with r1755098, but this time ensure the previous header processing logic 
ensures there was a previous header as identified by jchampion.

This patch restructures the loop for legibility with a loop continuation,
allowing us to flatten all of this hard-to-follow code. The subsequent
patch will be a whitespace-only change for formatting.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1755123 13f79535-47bb-0310-9956-ffa450edef68