Fix compile errors with MacOS (#312)

* Fix compile errors with MacOS
- _POSIX_C_SOURCE must not be defined for num_CPU()

* separate util_posix.c require changes in tools directory as well

* remove unnecessary self-include

client/util.h

@@ -77,16 +77,6 @@ extern void rol(uint8_t *data, const size_t len);
 
 extern void clean_ascii(unsigned char *buf, size_t len);
 
-// timer functions/macros
-#ifdef _WIN32
-# include <windows.h>
-# define sleep(n) Sleep(1000 *(n))
-# define msleep(n) Sleep((n))
-#else
-extern void msleep(uint32_t n);		// sleep n milliseconds
-#endif // _WIN32
-
-extern uint64_t msclock(); 			// a milliseconds clock
 extern int num_CPUs(void);			// number of logical CPUs
 
 #endif // UTIL_H__