[binutils-gdb] Add missing ATTRIBUTE_NORETURNs

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 621846f4e258167be2147894e013c85e42de1447 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 621846f4e258167be2147894e013c85e42de1447

Add missing ATTRIBUTE_NORETURNs

This patch adds a missing ATTRIBUTE_NORETURN.  This lets
-Wimplicit-fallthrough recognize that a given case does not fall
through.

ChangeLog
2018-05-04  Tom Tromey  <tom@tromey.com>

	* dwarf2loc.c (unimplemented): Add ATTRIBUTE_NORETURN.