base64: correct linkage of base64_maps_rfc4648

Two copies of this map meant only the tests would ever work.

ccan/base64/base64.c

@@ -209,7 +209,7 @@ ssize_t base64_decode_using_maps(const base64_maps_t *maps,
 /**
  * base64_maps_rfc4648 - pregenerated maps struct for rfc4648
  */
-static const base64_maps_t base64_maps_rfc4648 = {
+const base64_maps_t base64_maps_rfc4648 = {
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
 
   "\xff\xff\xff\xff\xff" /* 0 */					\

ccan/base64/base64.h

@@ -122,7 +122,7 @@ int base64_decode_tail_using_maps(const base64_maps_t *maps, char *dest,
 
 /* the rfc4648 functions: */
 
-static const base64_maps_t base64_maps_rfc4648;
+extern const base64_maps_t base64_maps_rfc4648;
 
 /**
  * base64_encode - Encode a buffer into base64 according to rfc4648