rfc822: Use the memmem module

This changes rfc822 to use the memmem module to supply a memmem() function
if the C library lacks it, instead of rolling our own locally.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/rfc822/_info

@@ -65,6 +65,7 @@ int main(int argc, char *argv[])
 		printf("ccan/list\n");
 		printf("ccan/str\n");
 		printf("ccan/bytestring\n");
+		printf("ccan/memmem\n");
 		return 0;
 	}
 

ccan/rfc822/rfc822.c

@@ -8,6 +8,7 @@
 #include <ccan/list/list.h>
 #include <stdio.h>
 
+#include <ccan/memmem/memmem.h>
 #include <ccan/rfc822/rfc822.h>
 
 #ifdef TAL_USE_TALLOC
@@ -16,24 +17,6 @@
 #include <ccan/tal/tal.h>
 #endif
 
-#if !HAVE_MEMMEM
-void *memmem(const void *haystack, size_t haystacklen,
-	     const void *needle, size_t needlelen)
-{
-	const char *p, *last;
-
-	p = haystack;
-	last = p + haystacklen - needlelen;
-
-	do {
-		if (memcmp(p, needle, needlelen) == 0)
-			return (void *)p;
-	} while (p++ <= last);
-
-	return NULL;
-}
-#endif
-
 static void (*allocation_failure_hook)(const char *);
 
 static void NORETURN default_allocation_failure(const char *s)