util-lib: split out allocation calls into alloc-util.[ch]

src/getty-generator/getty-generator.c

@@ -24,6 +24,7 @@
 #include <string.h>
 #include <unistd.h>
 
+#include "alloc-util.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "log.h"