update to 1.20.0 and enable qt6 build
    
    Update to 1.20.0 required for a poppler update and Qt6 builds for KDE Gear rpms using Plasma 6.

    

    The change is oriented on the archilinux build requiring a source copy and separate options compiling with qt5 or qt6.

    

    The qgpgme and qgpgme-devel packages have been changed for each build preserving build compaitbility with the qt5 use.

    qgpgme -> qgpgme-qt5

    qgpgpe-devel: slit into header files qpgpgme-common-devel and qgpgme-qt5-devel, qgpgme-qt6-devel for the Qt6 builds.

    

    When used with Qt6 builds, use BuildRequires: qgpgme-qt6-devel to draw in the right libs and dependencies.