Add non-TRUSTEDBSD prefixed knobs for the _PC_ACL* and {CAP,INF,MAC}_PRESENT knobs

It's not necessarily intuitive that the variables to query contain TRUSTEDBSD
in the prefix. Add non-TRUSTEDBSD prefixed knobs for querying things like
"_PC_ACL_NFS4".

MFC after: 1 week
Relnotes: yes
Reviewed by: wollman
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D7618