json: make json_add_string do partial escapes.

This is useful when we log a JSON-escaped string, so we don't double-escape.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

cli/Makefile

@@ -4,6 +4,7 @@ LIGHTNING_CLI_OBJS := $(LIGHTNING_CLI_SRC:.c=.o)
 LIGHTNING_CLI_COMMON_OBJS :=			\
 	common/configdir.o			\
 	common/json.o				\
+	common/json_escaped.o			\
 	common/version.o
 
 lightning-cli-all: cli/lightning-cli

cli/test/Makefile

@@ -12,6 +12,7 @@ CLI_TEST_COMMON_OBJS :=				\
 	common/daemon_conn.o			\
 	common/htlc_state.o			\
 	common/json.o				\
+	common/json_escaped.o			\
 	common/pseudorand.o			\
 	common/memleak.o			\
 	common/msg_queue.o			\