Add NetBSD support in sanitizer_syscall_generic.inc

Summary:
This adds:
 - NetBSD specific aliases for renamed syscalls,
 - differentiate internal_syscall, internal_syscall64, internal_syscall_ptr as there are various types of syscalls on NetBSD.

Part of the code inspired by the original work on libsanitizer in GCC 5.4 by Christos Zoulas.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, kcc, vitalybuka, filcab

Reviewed By: vitalybuka

Subscribers: kubamracek, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D36316

llvm-svn: 310139