i18n: New keywords for xgettext extraction from sh

Since we have additional shell wrappers (gettextln and eval_gettextln)
for gettext, we need to take into account these wrappers when running
'make pot' to extract messages from shell scripts.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Reviewed-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -2376,7 +2376,8 @@ XGETTEXT_FLAGS = \
 	--from-code=UTF-8
 XGETTEXT_FLAGS_C = $(XGETTEXT_FLAGS) --language=C \
 	--keyword=_ --keyword=N_ --keyword="Q_:1,2"
-XGETTEXT_FLAGS_SH = $(XGETTEXT_FLAGS) --language=Shell
+XGETTEXT_FLAGS_SH = $(XGETTEXT_FLAGS) --language=Shell \
+	--keyword=gettextln --keyword=eval_gettextln
 XGETTEXT_FLAGS_PERL = $(XGETTEXT_FLAGS) --keyword=__ --language=Perl
 LOCALIZED_C := $(C_OBJ:o=c) $(LIB_H) $(GENERATED_H)
 LOCALIZED_SH := $(SCRIPT_SH)