util: split out errno related stuff

src/libsystemd/sd-bus/bus-error.c

@@ -12,6 +12,7 @@
 #include "alloc-util.h"
 #include "bus-error.h"
 #include "errno-list.h"
+#include "errno-util.h"
 #include "string-util.h"
 #include "util.h"
 

src/libsystemd/sd-resolve/sd-resolve.c

@@ -16,6 +16,7 @@
 
 #include "alloc-util.h"
 #include "dns-domain.h"
+#include "errno-util.h"
 #include "fd-util.h"
 #include "io-util.h"
 #include "list.h"