Added mapping for pointers captured in Lambdas in OpenMP target regions,

by David Truby.

Summary:
This adds a zero length array section mapping for each pointer captured by a lambda that is used in a target region, as per section 2.19.7.1 of the OpenMP 5 specification.

Reviewers: ABataev

Reviewed By: ABataev

Subscribers: guansong, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64558

llvm-svn: 365777