gettext: switch to binary catalogs

Binary catalogs are more space efficient (total translations disk usage:
14MB instead of 35MB), and easier and faster (roughly 10 times) to load:
no parsing, and less processing (no need to unescape strings).

Not much difference on the Android APK size (a ~600KB reduction), but
other TAR.GZ / ZIP distributions see a reduction of ~3.5MB.

Makefile

@@ -1,4 +1,4 @@
-PHONY = all android-ndk android-sdk base clean distclean doc fetchthirdparty po pot re static-check
+PHONY = all android-ndk android-sdk base clean distclean doc fetchthirdparty re static-check
 SOUND = $(INSTALL_DIR)/%
 
 # koreader-base directory
@@ -81,6 +81,7 @@ ev_replay.py
 help
 history
 l10n/templates
+l10n/*/*.po
 ota
 resources/fonts*
 resources/icons/src*
@@ -134,7 +135,7 @@ $(foreach a,$1,'$(if $(filter --%,$a),$a,$(abspath $a))') $(or $2,koreader)
 $(call release_excludes,$(or $2,koreader)/)
 endef
 
-all: base
+all: base mo
 	install -d $(INSTALL_DIR)/koreader
 	rm -f $(INSTALL_DIR)/koreader/git-rev; echo "$(VERSION)" > $(INSTALL_DIR)/koreader/git-rev
 ifdef ANDROID
@@ -190,7 +191,7 @@ else
 	git submodule update --jobs 3 --init --recursive
 endif
 
-clean: base-clean
+clean: base-clean mo-clean
 	rm -rf $(INSTALL_DIR)
 
 distclean: clean base-distclean
@@ -209,31 +210,14 @@ ifneq (,$(wildcard make/$(TARGET).mk))
   include make/$(TARGET).mk
 endif
 
+include make/gettext.mk
+
 android-ndk:
 	$(MAKE) -C $(KOR_BASE)/toolchain $(ANDROID_NDK_HOME)
 
 android-sdk:
 	$(MAKE) -C $(KOR_BASE)/toolchain $(ANDROID_HOME)
 
-# for gettext
-DOMAIN=koreader
-TEMPLATE_DIR=l10n/templates
-XGETTEXT_BIN=xgettext
-
-pot: po
-	mkdir -p $(TEMPLATE_DIR)
-	$(XGETTEXT_BIN) --from-code=utf-8 \
-		--keyword=C_:1c,2 --keyword=N_:1,2 --keyword=NC_:1c,2,3 \
-		--add-comments=@translators \
-		reader.lua `find frontend -iname "*.lua" | sort` \
-		`find plugins -iname "*.lua" | sort` \
-		`find tools -iname "*.lua" | sort` \
-		-o $(TEMPLATE_DIR)/$(DOMAIN).pot
-
-po:
-	git submodule update --remote l10n
-
-
 static-check:
 	@if which luacheck > /dev/null; then \
 			luacheck -q {reader,setupkoenv,datastorage}.lua frontend plugins spec; \