decl.c (grokfndecl): Set DECL_CONTEXT on parms.

        cp/:
        * decl.c (grokfndecl): Set DECL_CONTEXT on parms.
        (duplicate_decls): Adjust DECL_CONTEXT of newdecl's parms.
        * pt.c (check_explicit_specialization): Likewise.
        (tsubst_copy) [PARM_DECL]: Return a dummy parm if we don't have a
        local specialization.
        * tree.c (cp_tree_equal) [PARM_DECL]: Check type and index, not name.
        * decl2.c (parm_index): New fn.
        * semantics.c (finish_decltype_type): Don't use describable_type.
        * mangle.c (write_expression): Likewise.  Mangle ALIGNOF_EXPR.
        Give a sorry for unsupported codes rather than crash.  Mangle
        conversions with other than 1 operand.  New mangling for PARM_DECL.
        * operators.def (ALIGNOF_EXPR): Mangle as az.
  
        * include/demangle.h (enum demangle_component_type): Add
        DEMANGLE_COMPONENT_FUNCTION_PARAM.
        * libiberty/cp-demangle.c (d_make_function_param): new fn.
        (cplus_demangle_mangled_name): Work around abi v2 bug.
        (d_expr_primary): Likewise.
        (cplus_demangle_operators): Add alignof ops.
        (d_expression): Handle function parameters and conversions
        with other than 1 operand.
        (d_print_comp): Handle function parameters.  Fix bug with
        function used in type of function.

From-SVN: r144924