gas: Use udata for DW_AT_high_pc when emitting DWARF4 (Was: Broken GAS DWARF tests)

[Alan Modra]

On Mon, Aug 03, 2020 at 10:11:27PM +0200, Mark Wielaard wrote:
>        * dwarf2dbg.c (out_debug_abbrev): When DWARF2_VERSION >= 4, use
>        DW_FORM_udata for DW_AT_high_pc.
>        (out_debug_info): Use emit_leb128_expr for DW_AT_high_pc, when
>        DWARF2_VERSION >= 4.
>        * read.c (emit_leb128_exp): No longer static.
>        * read.h (emit_leb128_exp): Define.

OK, looks good.  Note that there have been problems in the past
resolving leb128 expressions (eg. see 38cf168be581), so please keep an
eye out for regressions.

-- 
Alan Modra
Australia Development Lab, IBM