[18/18] comctl32: TaskDialog - Add ability to cancel dialog

[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=28889

Your paranoid android.


=== wxppro (32 bit taskdialog) ===
taskdialog.c:631: Test failed: TaskDialogIndirect not exported by name.

=== w2003std (32 bit taskdialog) ===
taskdialog.c:631: Test failed: TaskDialogIndirect not exported by name.

=== w7pro64 (64 bit taskdialog) ===
0718:taskdialog: unhandled exception c0000005 at 000000000046211E

=== w1064 (64 bit taskdialog) ===
0b44:taskdialog: unhandled exception c0000005 at 000000000046211E