Fixed missing prototypes and made it work with Solaris X11.

diff --git a/tsx11/ts_xf86vmode.c b/tsx11/ts_xf86vmode.c
index 78cb208..035404a 100644
--- a/tsx11/ts_xf86vmode.c
+++ b/tsx11/ts_xf86vmode.c
@@ -15,7 +15,9 @@
 
 #include <X11/Xlib.h>
 #include <X11/extensions/xf86vmode.h>
+
 #include "debugtools.h"
+#include "ts_xf86vmode.h"
 #include "x11drv.h"
 
 DEFAULT_DEBUG_CHANNEL(x11)