Improved capturing variable-length array types in CapturedStmt.

Improved capturing variable-length array types in CapturedStmt.
An updated implemnentation of VLA types capturing based on previously committed solution for Lambdas.
This version captures the whole VLA type instead of particular variables which are part of VLA size expression and allows to use previusly calculated size of VLA type in captured regions. Required for OpenMP.
Differential Revision: http://reviews.llvm.org/D5099

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220850 91177308-0d34-0410-b5e6-96231b3b80d8