Check correctness of BSA writing using official BSAs

[Ortham]

Reading in the official BSAs below then writing them out again and comparing input and output files can be used to check the correctness of libbsa's BSA writing code.

    List of official BSAs for testing.
    R = Reads OK, E = Extracts OK, W = Writes OK.
    !R = Doesn't read OK, !E and !W similar.

    Morrowind:
    Morrowind.bsa                           R   E   !W
    Bloodmoon.bsa                           R   E   !W
    Tribunal.bsa                            R   E   W

    Oblivion:
    Oblivion - Meshes.bsa                   R   E   !W
    Oblivion - Misc.bsa                     R   E   W
    Oblivion - Sounds.bsa                   R   E   W
    Oblivion - Textures - Compressed.bsa    R   E   W
    Oblivion - Voices1.bsa                  R   E   W
    Oblivion - Voices2.bsa                  R   E   W
    Knights.bsa                             R   E   !W
    DLCShiveringIsles - Meshes.bsa          R   E   !W
    DLCShiveringIsles - Sounds.bsa          R   E   W
    DLCShiveringIsles - Textures.bsa        R   E   !W
    DLCShiveringIsles - Voices.bsa          R   E   W

    Skyrim:
    Skyrim - Animations.bsa                 R   E   !W
    Skyrim - Interface.bsa                  R   E   W
    Skyrim - Meshes.bsa                     R   E   !W
    Skyrim - Misc.bsa                       R   E   !W
    Skyrim - Shaders.bsa                    R   E   !W
    Skyrim - Sounds.bsa                     R   E   W
    Skyrim - Textures.bsa                   R   E   !W
    Skyrim - Voices.bsa                     R   E   W
    Skyrim - VoicesExtra.bsa                R   E   W
    Update.bsa                              R   E   W