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

tools/mfkey/Makefile

@@ -4,7 +4,7 @@ LD = gcc
 CFLAGS = -std=c99 -D_ISOC99_SOURCE -I../../common -I../../client -Wall -O3
 LDFLAGS =
 
-OBJS = crypto1.o crapto1.o parity.o util.o mfkey.o
+OBJS = crypto1.o crapto1.o parity.o util_posix.o mfkey.o
 EXES = mfkey32 mfkey64
 WINEXES = $(patsubst %, %.exe, $(EXES))
 

tools/mfkey/mfkey32.c

@@ -4,7 +4,8 @@
 #include <stdlib.h>
 #include "crapto1/crapto1.h"
 #include "mfkey.h"
-#include "util.h"
+#include "util_posix.h"
+
 
 // 32 bit recover key from 2 nonces
 int main (int argc, char *argv[]) {

tools/mfkey/mfkey64.c

@@ -2,7 +2,7 @@
 #include <string.h>
 #include <inttypes.h>
 #include "crapto1/crapto1.h"
-#include "util.h"
+#include "util_posix.h"
 
 int main (int argc, char *argv[]) 
 {