[OPENMP50]Add support for 'parallel master taskloop' construct.

Added parsing/sema/codegen support for 'parallel master taskloop'
constructs. Some of the clauses, like 'grainsize', 'num_tasks', 'final'
and 'priority' are not supported in full, only constant expressions can
be used currently in these clauses.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374791 91177308-0d34-0410-b5e6-96231b3b80d8
41 files changed