user32/tests: Add message tests for EM_SETSEL when getting/losing focus in combo boxes (v2)

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=19336

Your paranoid android.


=== w7u (32 bit msg) ===
msg.c:4644: Test failed: ShowWindow(SW_RESTORE):overlapped: 18: the msg sequence is not complete: expected 0000 - actual 0088

=== w1064 (32 bit msg) ===
msg.c:6290: Test failed: Update region shouldn't be empty
msg.c:6524: Test failed: InvalidateErase: 0: the msg sequence is not complete: expected 0085 - actual 0000
msg.c:6526: Test failed: Paint: 0: the msg sequence is not complete: expected 000f - actual 0000
msg.c:6296: Test failed: Regions are different
msg.c:6296: Test failed: Regions are different
msg.c:6296: Test failed: Regions are different