Add option to specify special permissions for dumpcap during cmake phase:

Add option to specify special permissions for dumpcap during cmake phase:
set(DUMPCAP_INSTALL_OPTION   <val>)
where val is one of "normal" "suid" "capabilities"

Some things left to do:
- Error out in cmake if setcap isn't found or libcap isn't found.
- Move multivalue option handling into it's own macro (-file) with
  value checking

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@54840 f5534014-38df-0310-8fa8-9805f1628bb7