[OPENMP] Fixed codegen for 'copyprivate' clause.

Fixed initialization of 'single' region completion + changed type of the third argument of __kmpc_copyprivate() runtime function to size_t.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@236198 91177308-0d34-0410-b5e6-96231b3b80d8