i18n: git-am cannot_fallback messages

Translate messages with gettext(1) before they're passed to the
cannot_fallback function, just like we handle the die function.

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

git-am.sh

@@ -133,7 +133,7 @@ fall_back_3way () {
 	"$dotest/patch" &&
     GIT_INDEX_FILE="$dotest/patch-merge-tmp-index" \
     git write-tree >"$dotest/patch-merge-base+" ||
-    cannot_fallback "Repository lacks necessary blobs to fall back on 3-way merge."
+    cannot_fallback "$(gettext "Repository lacks necessary blobs to fall back on 3-way merge.")"
 
     say Using index info to reconstruct a base tree...
     if GIT_INDEX_FILE="$dotest/patch-merge-tmp-index" \
@@ -142,8 +142,8 @@ fall_back_3way () {
 	mv "$dotest/patch-merge-base+" "$dotest/patch-merge-base"
 	mv "$dotest/patch-merge-tmp-index" "$dotest/patch-merge-index"
     else
-        cannot_fallback "Did you hand edit your patch?
-It does not apply to blobs recorded in its index."
+	cannot_fallback "$(gettext "Did you hand edit your patch?
+It does not apply to blobs recorded in its index.")"
     fi
 
     test -f "$dotest/patch-merge-index" &&