i18n: git-stash drop_stash say/die messages

Gettextize the say/die eval_gettext messages in the drop_stash
function. Since making these translatable would result in a long line
I've wrapped this into two lines.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-stash.sh

@@ -430,7 +430,8 @@ drop_stash () {
 	assert_stash_ref "$@"
 
 	git reflog delete --updateref --rewrite "${REV}" &&
-		say "Dropped ${REV} ($s)" || die "${REV}: Could not drop stash entry"
+		say "$(eval_gettext "Dropped \${REV} (\$s)")" ||
+		die "$(eval_gettext "\${REV}: Could not drop stash entry")"
 
 	# clear_stash if we just dropped the last stash entry
 	git rev-parse --verify "$ref_stash@{0}" > /dev/null 2>&1 || clear_stash