Add interceptors for the sysctl(3) API family from NetBSD

Summary:
Add new interceptors for:

 - sysctl
 - sysctlbyname
 - sysctlgetmibinfo
 - sysctlnametomib
 - asysctl
 - asysctlbyname

Cover the API with a new test file TestCases/NetBSD/sysctl.cc.

Reviewers: joerg, vitalybuka

Reviewed By: vitalybuka

Subscribers: devnexen, kubamracek, llvm-commits, mgorny, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D54076

llvm-svn: 348228