insane.bbclass: Optimisation to speed up the package qa phase

insane.bbclass: Optimisation to speed up the package qa phase

    If you have a package with many data files (like xserver-xorg-print)
    the overhead of forking and executing scanelf/objdump on these files
    is way too high.

    Change the code to open the file and check if it is an elf file.
    Pass the result to the checking functions. If we do not have an elf
    file in front of us do not execute scanelf/objdump.

    This is a speed increase, it still detects GNU hash, the other parts
    should continue to work as well but needs some verificiation.