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* New header file "Hdr:UserIF.UserIF" provided for definitions specific to the user interface on products.  This abstracts the UI definitions from the machine-specific ones, and (ultimately) allows more flexibility in the choice of Machine and UserIF build combinations.

Detail:

  * As part of the work to remove the (almost obsolete) STB flag, a new
    flag has been defined: Embedded_UI.  This is provided by the "UserIF"
    header file.  The file should not be directly included; instead use the
    same mechanism as for "Hdr:Machine.Machine" and use "Hdr:UserIF.<UserIF>".

    In the past, the STB flag has been used to mean different things in
    different software components, some machine-dependent but more often than
    not to differentiate desktop builds from STB/NC versions.  Two types
    of system are identified: "Desktop" and "Embedded"; UserIF_Type is
    defined as a string containing the UI type.  STB/NC user interface
    differences should be encapsulated in appropriate "Embedded_UI" switc...