Upgrade to ASM 6.0

    Codebase migrated to gitlab (feature requests 317617, 317619, 317542)
    Support for modules (JSR 376, feature request 317628)
    Support for JDK specific module attributes (ModuleTarget, ModuleHashes and ModuleResolution).
    ASM jars now contain debug info, asm-all jar removed (feature request 317622)
    Support for removable features deleted (cf SIGNATURES, ANNOTATIONS, etc constants in ClassReader)
    bug fixes
        317793: AnalyzerAdapter calculates wrong type for AALOAD in case of null
        317784: NegativeArraySizeException when resizing jump instruction in a class without frames
        317780: IllegalArgumentException at CheckMethodAdapter.checkInternalName for non-Java-identifier name
        317785: NullPointerException in MethodRemapper with 'chop' stack map frames and tree API
        317786: VerifyError when added code pushes the offset of a conditional backward jump below -32768
        317791: Invalid class files generated for large methods (regression introduced in 5.2)
        317792: Fix the handling of inner classes with EXPAND_ASM_INSNS
        Bug fix related to stack map frames