Add new interceptors for FILE repositioning stream

Summary:
Add new interceptors for a set of functions to reposition a stream:
fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind .

Add a dedicated test.

Enable this interface on NetBSD.

Reviewers: joerg, vitalybuka

Reviewed By: vitalybuka

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

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D55471

llvm-svn: 348743