Sync libiberty and include with GCC for get_DW_UT_name.

Sync libiberty and include with GCC for get_DW_UT_name.

This adds a get_DW_UT_name function to dwarfnames using dwarf2.def
for use in binutils readelf to show the unit types in a DWARF5 header.

include/ChangeLog:

	Sync with GCC
	* dwarf2.def: Add DWARF5 Unit type header encoding macros
	DW_UT_FIRST, DW_UT and DW_UT_END.
	* dwarf2.h (enum dwarf_unit_type): Removed and define using
	DW_UT_FIRST, DW_UT and DW_UT_END macros.
	(get_DW_UT_name): New function declaration.

libiberty/ChangeLog:

	Sync with GCC
	* dwarfnames.c (get_DW_UT_name): Define using DW_UT_FIRST, DW_UT
	and DW_UT_END.

(cherry picked from commit d7b477c541bd31045483f37345727bd8335a052a)