config: parallel-safe param.h makefile rule

Generate the param.h.new temporary file in a parallel-safe
way.  The rule to generate the three copies of param.h can
run at the the same time under a parallel make, clobbering
the param.h.new temporary file. Instead of creating this file
inline, create a common rule to generate the temporary file
once.

Reviewed-on: http://gerrit.openafs.org/10516
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit c8e83f0e826bc0a56321408b1c7a2afa137bab05)

Change-Id: I8a85c0e288f2231a3bf693319a8f5fcd618464e8
Reviewed-on: http://gerrit.openafs.org/11229
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>