Replace DARWIN macro with __APPLE__

As discussed on https://github.com/hashcat/hashcat/pull/409

include/common.h

@@ -45,7 +45,7 @@
 #include <sys/ioctl.h>
 #endif
 
-#ifdef DARWIN
+#ifdef __APPLE__
 #include <termios.h>
 #include <sys/ioctl.h>
 #include <mach-o/dyld.h>
@@ -64,7 +64,7 @@ typedef void *ADL_LIB;
 typedef void *NVAPI_LIB;
 typedef void *NVML_LIB;
 typedef void *XNVCTRL_LIB;
-#ifdef DARWIN
+#ifdef __APPLE__
 #define __stdcall
 #endif
 #endif

include/ext_OpenCL.h

@@ -13,7 +13,7 @@
 #define CL_USE_DEPRECATED_OPENCL_1_2_APIS
 #define CL_USE_DEPRECATED_OPENCL_2_0_APIS
 
-#ifdef DARWIN
+#ifdef __APPLE__
 #include <OpenCL/cl.h>
 #endif
 

include/shared.h

@@ -46,7 +46,7 @@
 #define hc_thread_mutex_delete(m)   pthread_mutex_destroy  (&m)
 #endif
 
-#ifdef DARWIN
+#ifdef __APPLE__
 typedef struct cpu_set
 {
   uint32_t count;