Added URL to error message
Let configure abort in case needed header files cannot be found
Resolve ambiguous log messages in case of backend errors
Don't mix request_rec pool and backend connection bucket allocator in brigade

Mixing request_rec pool and backend connection bucket allocator in
apr_brigade_create() leads to a segmentation fault if the brigade is
accessed after the request record was destroyed.
raise log level to error for unexpected backend response

It's important to know if the backend server doesn't respond according to
the pattern "HTTP/1.1 ###*" (eg. "HTTP/1.0 503 ..." if there is a problem
with the Exchange server name in the request). So raised the log level for
the corresponding message from info to error.
Log request headers in log level TRACE3
Get some more debugging information about used authentication mechanisms
Fix link order of test binary to resolve build failure

Thanks to Daniel T Chen <crimsun@ubuntu.com> for providing the patch via Ubuntu.
Remove unneeded linker flags in compile-only make target
Merge tag 'mod_proxy_msrpc-0.5' into debian/unstable
Prepare upload of 0.5-1 to Debian unstable