README.txt: Improve sample code

- use hid_init()/hid_exit()
- include windows.h only on Windows

README.txt

@@ -46,7 +46,9 @@ which communicates with a heavily hacked up version of the Microchip USB
 Generic HID sample looks like this (with error checking removed for
 simplicity):
 
+#ifdef WIN32
 #include <windows.h>
+#endif
 #include <stdio.h>
 #include <stdlib.h>
 #include "hidapi.h"
@@ -61,6 +63,9 @@ int main(int argc, char* argv[])
 	hid_device *handle;
 	int i;
 
+	// Initialize the hidapi library
+	res = hid_init();
+
 	// Open the device using the VID, PID,
 	// and optionally the Serial number.
 	handle = hid_open(0x4d8, 0x3f, NULL);
@@ -92,12 +97,15 @@ int main(int argc, char* argv[])
 	res = hid_write(handle, buf, 65);
 
 	// Read requested state
-	hid_read(handle, buf, 65);
+	res = hid_read(handle, buf, 65);
 
 	// Print out the returned buffer.
 	for (i = 0; i < 4; i++)
 		printf("buf[%d]: %d\n", i, buf[i]);
 
+	// Finalize the hidapi library
+	res = hid_exit();
+
 	return 0;
 }