Various fixes submitted by Yaakov Selkowitz (RHBZ #1048677)
    
    - Fix qmake to use .dll.a extension for implibs (avoids renaming hacks
      in all mingw-qt5-* packages)
    - Force usage of system zlib in Qt5Bootstrap
    - Install shared libQt5BootstrapDBus for qdbuscpp2xml and qdbusxml2cpp
    - Fix QMAKE_LIBS_NETWORK for static linkage