Define WCOREDUMP in salvsync-server.c

Define WCOREDUMP in salvsync-server.c

Some platforms do not define WCOREDUMP. Conditionally define WCOREDUMP
in salvsync-server.c, and make all of the similar WCOREDUMP defines in
the tree consistent.

Change-Id: I197979881ade20f6e790bf41523938089379dbe3
Reviewed-on: http://gerrit.openafs.org/846
Reviewed-by: Russ Allbery <rra@stanford.edu>
Reviewed-by: Tom Keiser <tkeiser@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>