fix UB...

it's promoted to int (signed) which when shifting into the sign bit is
UB per §6.5.7 ¶ 4 of the C99 spec.

irr_main.c

@@ -159,7 +159,7 @@ analog_seed_rng(void)
 static inline uint32_t
 letoh_32(uint8_t *v)
 {
-	return v[0] | (v[1] << 8) | (v[2] << 16) | (v[3] << 24);
+	return v[0] | (v[1] << 8) | (v[2] << 16) | ((unsigned)v[3] << 24);
 }
 
 struct chaninfo {