Add new interceptors: getttyent(3) family

Summary:
getttyent, getttynam, setttyentpath - get ttys file entry

Reuse them on NetBSD.

Sponsored by <The NetBSD Foundation>

Reviewers: vitalybuka, joerg

Reviewed By: vitalybuka

Subscribers: llvm-commits, kubamracek, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D43539

llvm-svn: 326161