Don't put hyphens in the rc's versions.

Apparently neither RPM nor the Debian packaging systems like having hyphens in
in the version.

This change leaves a hyphen in the daily builds (which means we can't build
RPMs or .debs of those); we might want to consider changing that to a tilde
(~).

Change-Id: Iaa4f3135e9e6452c2e1e199d85540e50778c5cdc
Reviewed-on: https://code.wireshark.org/review/2759
Reviewed-by: Gerald Combs <gerald@wireshark.org>