Now that we can get information about an actual arg's associated
dummy using the associated_dummy attribute, the field missing_arg_type
contains redundant information.
This removes it.
gcc/fortran/ChangeLog:
* gfortran.h (gfc_actual_arglist::missing_arg_type): Remove.
* interface.c (gfc_compare_actual_formal): Remove
missing_arg_type initialization.
* intrinsic.c (sort_actual): Ditto.
* trans-expr.c (gfc_conv_procedure_call): Use associated_dummy
and gfc_dummy_arg_get_typespec to get the dummy argument type.