devtools/print_wire: add return for numerical fields.

Before:
    $ ./devtools/decodemsg 0102c2bd3f4a94ff390ce764caf51925d0ed38fa95b6539945b42124f5c4e625da63351380c79230a05550d0e5def9c2412f4f164478f9f9491140e505f79c0d716506226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73cf188910f00006700000100015afd0da1000000060000000000000000000000010000000a
    WIRE_CHANNEL_UPDATE:
    signature=3045022100c2bd3f4a94ff390ce764caf51925d0ed38fa95b6539945b42124f5c4e625da630220351380c79230a05550d0e5def9c2412f4f164478f9f9491140e505f79c0d7165
    chain_hash=0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206
    short_channel_id=103:1:1
    timestamp=1526533537flags=0cltv_expiry_delta=6htlc_minimum_msat=0fee_base_msat=1fee_proportional_millionths=10

After:

    WIRE_CHANNEL_UPDATE:
    signature=3045022100c2bd3f4a94ff390ce764caf51925d0ed38fa95b6539945b42124f5c4e625da630220351380c79230a05550d0e5def9c2412f4f164478f9f9491140e505f79c0d7165
    chain_hash=0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206
    short_channel_id=103:1:1
    timestamp=1526533537
    flags=0
    cltv_expiry_delta=6
    htlc_minimum_msat=0
    fee_base_msat=1
    fee_proportional_millionths=10

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

devtools/print_wire.c

@@ -5,22 +5,22 @@
 
 void printwire_u8(const u8 *v)
 {
-	printf("%u", *v);
+	printf("%u\n", *v);
 }
 
 void printwire_u16(const u16 *v)
 {
-	printf("%u", *v);
+	printf("%u\n", *v);
 }
 
 void printwire_u32(const u32 *v)
 {
-	printf("%u", *v);
+	printf("%u\n", *v);
 }
 
 void printwire_u64(const u64 *v)
 {
-	printf("%"PRIu64, *v);
+	printf("%"PRIu64"\n", *v);
 }
 
 void printwire_u8_array(const u8 **cursor, size_t *plen, size_t len)