tests: Include system headers appropriately

Don't include unistd.h on Windows, and include the appropriate headers on
Windows as necessary.

https://bugzilla.gnome.org/show_bug.cgi?id=773299

tests/testanimation.c

@@ -19,11 +19,14 @@
 #include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <string.h>
 #include <errno.h>
 #include <gtk/gtk.h>
 
+#ifndef G_OS_WIN32
+# include <unistd.h>
+#endif
+
 typedef struct _LoadContext LoadContext;
 
 struct _LoadContext

testsuite/a11y/accessibility-dump.c

@@ -25,6 +25,10 @@
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
 
+#ifdef G_OS_WIN32
+# include <io.h>
+#endif
+
 #define DEPTH_INCREMENT 2
 
 static char *

testsuite/css/nodes/test-css-nodes.c

@@ -22,6 +22,10 @@
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
 
+#ifdef G_OS_WIN32
+# include <io.h>
+#endif
+
 
 static char *
 test_get_reference_file (const char *ui_file)

testsuite/css/parser/test-css-parser.c

@@ -26,6 +26,10 @@
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
 
+#ifdef G_OS_WIN32
+# include <io.h>
+#endif
+
 static char *
 test_get_reference_file (const char *css_file)
 {

testsuite/css/style/test-css-style.c

@@ -22,6 +22,10 @@
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
 
+#ifdef G_OS_WIN32
+# include <io.h>
+#endif
+
 /* There shall be no other styles */
 #define GTK_STYLE_PROVIDER_PRIORITY_FORCE G_MAXUINT
 

testsuite/reftests/gtk-reftest.c

@@ -28,6 +28,10 @@
 #include <glib/gstdio.h>
 #include <gtk/gtk.h>
 
+#ifdef G_OS_WIN32
+# include <direct.h>
+#endif
+
 typedef enum {
   SNAPSHOT_WINDOW,
   SNAPSHOT_DRAW