demangle.h (enum demangle_component_type): Add DEMANGLE_COMPONENT_DECLTYPE.

        * include/demangle.h (enum demangle_component_type): Add
        DEMANGLE_COMPONENT_DECLTYPE.
        * libiberty/cp-demangle.c (d_dump): Handle DEMANGLE_COMPONENT_DECLTYPE.
        (d_make_comp): Likewise.
        (cplus_demangle_type): Handle decltype and DFP types.
        (cplus_demangle_operators): Call operator takes 2 args.
        (cplus_demangle_builtin_types): Add DFP types.
        (d_exprlist): New fn.
        (d_expression): Handle parm placeholders, T() and calls.
        (d_print_comp): Handle decltype, T() and calls.
        * libiberty/testsuite/demangle-expected: Test the above.

From-SVN: r140162