Fix wrong android versionName

Before, android versionName was set to "...13", which made the f-droid build fail.

build/android/Makefile

@@ -867,7 +867,7 @@ $(ROOT)/jni/src/android_version.h : prep_srcdir
 	fi
 
 manifest :
-	@BASE_VERSION="${VERS_MAJOR}.${VERS_MINOR}.${VERS_PATCH}";                 \
+	@BASE_VERSION="${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}";        \
 	if [ "${NDEBUG}x" != "x" ] ; then                                          \
 		DBG='';                                                                \
 		DBG_FLAG="android:debuggable=\"false\"";                               \