Rx: cleanup testclient and testserver test applications

Rx: cleanup testclient and testserver test applications

Permit testclient and testserver to be built on Windows as
pthreaded applications.

Remove warnings.  Fix prototypes.  Remove variable declarations
for rx library variables defined in rx_globals.h.

Increase the buffer sizes.  Disable use of packet dropping when
the library is built without RXDEBUG.

Change-Id: Ic8483eb64cbed4958baf8fd054e01c7c40832599
Reviewed-on: http://gerrit.openafs.org/2780
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>