This allows write_conf_or_var_desc to have the context enabling it to
write out an appropriate correlation descriptor when iid_is is used
from within a structure.

widl: Use typegen_detect_type to determine which types should be written for the pointer description in write_struct_tfs.

Otherwise extra pointers for user types could be written.

widl: Don't use the return value of write_embedded_types to determine whether a type contains pointers or not.

It isn't correct in all situations, so type_has_pointer has to be used
anyway so using the return value of write_embedded_types just clutters
the code.

Avoid duplicating the pointer writing code.

The check for whether a pointer is the last one is redundant since
typegen_detect_type does a stricter check on the ref type. Replace one
other instance of last_ptr with a more readable equivalent.

Change write_pointer_tfs to rely on the detected type of the type to
determine when to write a simple pointer rather than relying on
typestring_offset not being set anywhere else.

Just add a context to the device's context array.

Our pbuffer support is broken, nobody cares.

dxdiagn: Fix string copy behavior with an excessively short buffer in IDxDiagContainer::EnumPropNames.

dxdiagn: Fix dot parsing in IDxDiagContainer::GetChildContainer for the case of a lone dot terminator.