Replace sprintf()->snprintf() and strcpy()->strlcpy()

The strcpy() and sprintf() functions are deprecated on some platforms.
Care is needed to ensure correct size is used.  If some platforms
miss snprintf, we can add a #define to sprintf, likewise strlcpy().

The biggest change is adding a size parameter to zfs_id_to_fuidstr().

The various *_impl_get() functions are only used on linux and have
not yet been updated.

module/icp/algs/aes/aes_impl.c

@@ -330,7 +330,7 @@ aes_impl_init(void)
 	    sizeof (aes_fastest_impl));
 #endif
 
-	strcpy(aes_fastest_impl.name, "fastest");
+	strlcpy(aes_fastest_impl.name, "fastest", AES_IMPL_NAME_MAX);
 
 	/* Finish initialization */
 	atomic_swap_32(&icp_aes_impl, user_sel_impl);
@@ -405,7 +405,7 @@ aes_impl_set(const char *val)
 	return (err);
 }
 
-#if defined(_KERNEL)
+#if defined(_KERNEL) && defined(__linux__)
 #include <linux/mod_compat.h>
 
 static int