build: exclude LMDB utilities from Windows CMake build, guard POSIX includes in mplay.c

file(GLOB) in libutun/CMakeLists.txt picked up mplay.c, mdb_dump.c and other
standalone LMDB tools that are not library code and fail on Windows. Filter them
out, keep only mdb.c + midl.c.

lib/liblmdb/mplay.c

@@ -13,13 +13,15 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <time.h>
 #include <string.h>
 #include <ctype.h>
 #include <assert.h>
+#ifndef _WIN32
+#include <unistd.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#endif
 
 #include "lmdb.h"