[16/18] comctl32: Taskdialog - Implement TDM_ENABLE_BUTTON and add tests

[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=28887

Your paranoid android.


=== wxppro (32 bit taskdialog) ===
taskdialog.c:531: Test failed: TaskDialogIndirect not exported by name.

=== w2003std (32 bit taskdialog) ===
taskdialog.c:531: Test failed: TaskDialogIndirect not exported by name.

=== w7pro64 (64 bit taskdialog) ===
0438:taskdialog: unhandled exception c0000005 at 000000000046211E

=== w864 (64 bit taskdialog) ===
0f54:taskdialog: unhandled exception c0000005 at 000000000046211E

=== w1064 (64 bit taskdialog) ===
0e44:taskdialog: unhandled exception c0000005 at 000000000046211E