simplify 'new_callback' op

[jimmy]

Hello,

I would like to simplify 'new_callback' op. first please see  https://github.com/parrot/parrot/blob/master/t/pmc/nci.t#L1545-#L1606-1551. there are lines:

    .local pmc user_data
    user_data = new ['Integer']
    user_data = 42

    # A Sub that can be given to the library
    # this callback function will eventually by called by the library
    .const 'Sub' cb = "_call_back"
    .local pmc cb_wrapped
    cb_wrapped = new_callback cb, user_data, "vtU"  # Z in pdd16
    print "created a callback sub\n"

    # now call the external sub, that takes a callback and user data
    .local pmc libnci_test
    libnci_test = loadlib "libnci_test"
    .local pmc nci_cb_C1
    nci_cb_C1 = dlfunc libnci_test, "nci_cb_C1", "vpP"
    print "loaded a function that takes a callback\n"
    nci_cb_C1( cb_wrapped, user_data )

passing the value of user_data into new_callback is useless and unused, because it's finally invoked and used by this code:

nci_cb_C1( cb_wrapped, user_data )

So consider:

    .local pmc user_data
    user_data = new ['Integer']

    # A Sub that can be given to the library
    # this callback function will eventually by called by the library
    .const 'Sub' cb = "_call_back"
    .local pmc cb_wrapped
    user_data = 42
    cb_wrapped = new_callback cb, user_data, "vtU"  # Z in pdd16
    print "created a callback sub\n"

    # now call the external sub, that takes a callback and user data
    .local pmc libnci_test
    libnci_test = loadlib "libnci_test"
    .local pmc nci_cb_C1
    nci_cb_C1 = dlfunc libnci_test, "nci_cb_C1", "vpP"
    print "loaded a function that takes a callback\n"
    user_data = 44   # user_data is changed here.
    nci_cb_C1( cb_wrapped, user_data )

so passing user_data = 42 to new_callback is redundant, I would like to simplify it to this one:

    cb_wrapped = new_callback cb, "vtU"