The current GetProcAddress implementation only resolves functions in
DLLs by name. Add GetProcAddressByOrdinal that allows resolving
functions by ordinal number, using the same GetProcAddress call from
kernel32.dll in the background.

This is particularly useful for some functions (e.g. IsOS from
shlwapi.dll in some older versions of Windows) that cannot be found by
name.

Fixes golang/go#16507

Change-Id: Ib5fba7568c365a0aa2491c1261876b3a3929ec3d
Reviewed-on: https://go-review.googlesource.com/70690Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>