Fix NtUserOpenClipboard

[diversenok]

This pull request updates the definition for NtUserOpenClipboard to reflect that the syscall writes to a pointer provided in the second argument. OpenClipboard passes an address of a local variable to this parameter and then reads from it, causing the following warning:

Error #1: UNINITIALIZED READ: reading 0x00000092296ff998-0x00000092296ff99c 4 byte(s)
# 0 USER32.dll!OpenClipboard
# 1 main                        
Note: @0:00:00.082 in thread 11352
Note: instruction: cmp    0x38(%rsp) $0x00000000

Similar changes would apply to the following files in the dynamorio submodule; not sure if you want me to create a separate pull request to address that:

dynamorio\ext\drsyscall\table_windows_ntuser.c
dynamorio\ext\drmf\wininc\ntuser.h

[derekbruening]

Thank you for the PR!

Unfortunately the tests may have issues due to Github dropping support for the Linux and Windows VM versions used...but should be good to merge.

[derekbruening]

Similar changes would apply to the following files in the dynamorio submodule; not sure if you want me to create a separate pull request to address that:
dynamorio\ext\drsyscall\table_windows_ntuser.c
dynamorio\ext\drmf\wininc\ntuser.h

Yes, we will need the same changes there, as DynamoRIO/dynamorio#7303 did not yet remove drsyscall from drmemory/ (note to @ivankyluk) and the dynamorio/ copy is what is used outside of drmemory now.