Restore thread if there's no interrupt handler set.

If dispatch is disabled and we don't do this, it'll just hang, never
switching back to a thread that can re-enable dispatch.

Fixes #5172.
Abort on a message dialog just moves to finished.

Still need to shutdown.  Fixes #5177.
Set msgdialog result to 0 after displayed.

This might fix anything checking the result code without zeroing it first.
Merge pull request #5180 from unknownbrackets/msgdialog

Fix aborting msgdialogs
Fix "Integer divide by zero 0"  in Spline.cpp
Merge pull request #5182 from sum2012/patch-2

Fix "Integer divide by zero"  in Spline.cpp
Win32: Use a hacky workaround to prevent a rare hang when starting up.
Make the bool a class member instead.
Merge pull request #5184 from thedax/win32RareHangHack

Win32: Use a hacky workaround to prevent a rare hang when starting up.
Blackberry: Remove narrow_landscape_exit as it restricts the usage of 'back' gestures on new installs.
Thanks for report Arifin.
Fix savestates from before v0.9.6-536-g62e9e42.

Unfortunately, this breaks savestates made since then until this is
merged.  However, that's only a day or so.

Fixes #5183.
Now umd0: size is in sectors, not bytes.

So we have to check based on that correctly.  Darn it.
Merge pull request #5187 from unknownbrackets/io-fix

Now umd0: size is in sectors, not bytes
Merge pull request #5186 from unknownbrackets/savestates

Fix savestates from before v0.9.6-536-g62e9e42
Merge pull request #5174 from unknownbrackets/intr-fix

Restore thread if there's no interrupt handler set
Oops, only reset MsgDialog result on success.
Validate options in MsgDialog v3 per tests.
Allow msgdialog override of ok/cancel button text.

Per tests, and hints from JPCSP.
Merge pull request #5188 from unknownbrackets/msgdialog

Clean up some more minor things in message dialogs