[OPENMP] Enable c++ exceptions outside of the target constructs iff they are

[OPENMP] Enable c++ exceptions outside of the target constructs iff they are
enabled for the host.

If the compilation for the host enables C++ exceptions, but they are not
supported by the device, we still need to allow the code with the
exception handling constructs outside of the target regions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@331372 91177308-0d34-0410-b5e6-96231b3b80d8