Use stable branch of libsodium

.gitmodules

@@ -30,6 +30,7 @@
 [submodule "mobile/src/main/jni/libsodium"]
 	path = mobile/src/main/jni/libsodium
 	url = https://github.com/jedisct1/libsodium.git
+	branch = stable
 [submodule "mobile/src/main/jni/libev"]
 	path = mobile/src/main/jni/libev
 	url = https://github.com/shadowsocks/libev.git

mobile/src/main/jni/Android.mk

@@ -26,7 +26,6 @@ include $(CLEAR_VARS)
 
 SODIUM_SOURCE := \
 	crypto_aead/chacha20poly1305/sodium/aead_chacha20poly1305.c \
-	crypto_aead/xchacha20poly1305/sodium/aead_xchacha20poly1305.c \
 	crypto_auth/crypto_auth.c \
 	crypto_auth/hmacsha256/auth_hmacsha256_api.c \
 	crypto_auth/hmacsha256/cp/hmac_hmacsha256.c \

mobile/src/main/res/values/arrays.xml

@@ -20,7 +20,6 @@
         <item>AES-256-GCM</item>
         <item>CHACHA20-POLY1305</item>
         <item>CHACHA20-IETF-POLY1305</item>
-        <item>XCHACHA20-IETF-POLY1305</item>
     </string-array>
 
     <string-array name="enc_method_value">
@@ -43,7 +42,6 @@
         <item>aes-256-gcm</item>
         <item>chacha20-poly1305</item>
         <item>chacha20-ietf-poly1305</item>
-        <item>xchacha20-ietf-poly1305</item>
     </string-array>
 
     <string-array name="route_entry">