Added support for setting read timeouts for backend requests
(first_byte_timeout and between_bytes_timeout), in addition to make the
connect_timeout available for the bereq object in vcl_miss and vcl_fetch.

first_byte_timeout is a read timeout from the connection to the backend is
created to when the first byte arrives. It can be set as a parameter to
varnish, as a field in the backend declaration or as bereq.first_byte_timeout
in vcl_miss and vcl_pass.

between_bytes_timeout is a read timeout between each read from the backend. It
can be set as a parameter to varnish, as a field in the backend declaration or
as bereq.between_bytes_timeout in vcl_miss and vcl_pass.

The time unit for these timeout values are seconds. NOTE: The connect_timeout
previously used milliseconds as time unit, so beware.



git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@3616 d4fa192b-c00b-0410-8231-f00ffab90ce4