util: split out memcmp()/memset() related calls into memory-util.[ch]

Just some source rearranging.

src/basic/alloc-util.c

@@ -5,7 +5,7 @@
 
 #include "alloc-util.h"
 #include "macro.h"
-#include "util.h"
+#include "memory-util.h"
 
 void* memdup(const void *p, size_t l) {
         void *ret;