Eliminated the use of AP_MODE_SPECULATIVE brigade reads to check

Eliminated the use of AP_MODE_SPECULATIVE brigade reads to check
for request header continuation lines.  Instead, ap_get_mime_headers_core()
now sets aside each line of input until it sees the next line.  If the
next line starts with a tab, it is appended to the previous one; otherwise,
the previous line is added to the request headers table.

This reduces the number of temporary buckets that must be created
and destroyed to read in a request.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95964 13f79535-47bb-0310-9956-ffa450edef68