Disabled testing the focus and foreground windows after creating the device
for the moment.

For some reason Windows XP allows device creation to be blocked by the lack of
message processing in wndproc_thread(). Thanks to Wylda for helping debug
this. Disabled testing the focus and foreground windows after creating the
device for the moment.

crypt32: Use an empty string as a separator when no separator is desired to avoid special cases for NULL.

This mirrors Dan Kegel's fix for iphlpapi.

dxdiagn: Successfully copy to destination variants with an invalid type in IDxDiagContainer::GetProp.

GetProp now simply unconditionally clears the destination variant if
VariantClear fails.