Consistently use the _WIN32 #define.

The _WIN32 variant is available pretty much on all compilers, others
might not be. G_OS_WIN32 would probably be an equally well-suited
alternative, but for now we standardize on _WIN32.

  http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system#WindowswithCygwinPOSIX

src/hardware/ipdbg-la/protocol.c

@@ -23,19 +23,15 @@
 #define _WIN32_WINNT 0x0501
 #include <winsock2.h>
 #include <ws2tcpip.h>
-#endif
-
-#include <string.h>
-#include <unistd.h>
-
-#ifndef _WIN32
+#else
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <sys/ioctl.h>
 #endif
-
+#include <string.h>
+#include <unistd.h>
 #include <errno.h>
 #include "protocol.h"
 
@@ -69,7 +65,7 @@
 
 static gboolean data_available(struct ipdbg_la_tcp *tcp)
 {
-#ifdef __WIN32__
+#ifdef _WIN32
 	u_long bytes_available;
 	ioctlsocket(tcp->socket, FIONREAD, &bytes_available);
 	return (bytes_available > 0);

src/libsigrok-internal.h

@@ -745,7 +745,7 @@ struct drv_context {
 
 /*--- log.c -----------------------------------------------------------------*/
 
-#if defined(G_OS_WIN32) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4))
+#if defined(_WIN32) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4))
 /*
  * On MinGW, we need to specify the gnu_printf format flavor or GCC
  * will assume non-standard Microsoft printf syntax.

src/serial.c

@@ -28,7 +28,7 @@
 #include <libserialport.h>
 #include <libsigrok/libsigrok.h>
 #include "libsigrok-internal.h"
-#ifdef G_OS_WIN32
+#ifdef _WIN32
 #include <windows.h> /* for HANDLE */
 #endif
 
@@ -788,7 +788,7 @@ SR_PRIV int sr_serial_extract_options(GSList *options, const char **serial_devic
 }
 
 /** @cond PRIVATE */
-#ifdef G_OS_WIN32
+#ifdef _WIN32
 typedef HANDLE event_handle;
 #else
 typedef int event_handle;

src/session.c

@@ -1294,7 +1294,7 @@ SR_PRIV int sr_session_source_add_channel(struct sr_session *session,
 	/* We should be using g_io_create_watch(), but can't without
 	 * changing the driver API, as the callback signature is different.
 	 */
-#ifdef G_OS_WIN32
+#ifdef _WIN32
 	g_io_channel_win32_make_pollfd(channel, events, &pollfd);
 #else
 	pollfd.fd = g_io_channel_unix_get_fd(channel);

src/usb.c

@@ -184,7 +184,7 @@ static LIBUSB_CALL void usb_pollfd_added(libusb_os_handle fd,
 		return;
 
 	pollfd = g_slice_new(GPollFD);
-#ifdef G_OS_WIN32
+#ifdef _WIN32
 	events = G_IO_IN;
 #endif
 	pollfd->fd = (gintptr)fd;