procmgmt: wrappers for softsig handlers

procmgmt: wrappers for softsig handlers

Provide procmgmt wrappers for Windows environments which match the opr_softsig
functions. This allows builds of the windows servers continue to use the
existing process management signal handling functions, without introducing
additional conditional compilation in the server code.

Change-Id: I0ac287bde294996fb7f32c19370f2992a0af2a58
Reviewed-on: https://gerrit.openafs.org/12236
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>