Currently, cl_khr_external_semaphore and cl_khr_external_memory define properties
to specify external win32 NT handle via pointer. Win32 NT handles can also be specified
via named strings.

Add properties to specify external Win32 NT handles via named strings too.

Fixes #943

Address review comments.

Fixes #943

* Updates to win32 named handle type changes.

Address review comments.

Fixes #943

* Drop NULL from named win32 handle description.

Address review comments from Ben to remove NULL
from named win32 handle description.

Fixes #943

Bump up spec versions for
cl_khr_external_memory_win32 from 1.0.0 to 1.1.0
and cl_khr_external_semaphore_win32 from 0.9.0 to 0.9.1

 Fix typo during conflict resolution opencl_runtime_layer.asciidoc.