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

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@365777 91177308-0d34-0410-b5e6-96231b3b80d8