qmgr: Implement the IUnknown interface for IBackgroundCopyJob and stubs for the rest of the methods.

imm32: Destroy the data of the context passed into ImmDestroyContext,  not the data in the root context.

Window and class DCEs are now allocated lazily.

avifil32: Fix the character count passed into LoadStringW in AVIBuildFilterW and AVISaveOptionsUpdate.

len is used in RegEnumKeyExW and this takes a character count for the 
key argument, not a byte count.

The number of remaining characters should be passed in, not the total 
buffer size.