More refactoring of ap_read_request() in preparation for

nonblocking read support.

WARNING: The code for handlng requests that exceed the field-length
or number-of-fields limits isn't complete in this commit.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/async-read-dev@349348 13f79535-47bb-0310-9956-ffa450edef68