winhelp: Fix the loading of a row in a table (especially, for multiple paragraphs in a single cell).

winhelp: Added the notion of WINHELP_WNDPAGE and use it to move the history to the global variables.

winhelp: Get rid of the reuse concept for Windows and refactor the code a bit for window creation / deletion.

widl: Remove duplicated code in the form of the write_struct_expr function by enhancing write_expr to allow toplevel identifiers to be prefixed by a string, if specified.

Remove the conversion of pointer types into base types as this was only 
needed due to lack of proper type resolving.

Also check that expressions return the correct type for the attribute.

widl: Pass the actual type into check_remoting_fields and check_field_common instead of the type name.