Resolves a test compatibility issue with xorg >= 1.19.

Upstream bug report:

https://sourceforge.net/p/linuxwacom/bugs/329/

Patch copied from upstream source repository:

https://sourceforge.net/p/linuxwacom/xf86-input-wacom/ci/f0dedf7a610ac97bc45738492b98ce4f1e0514ec/

From f0dedf7a610ac97bc45738492b98ce4f1e0514ec Mon Sep 17 00:00:00 2001
From: Jason Gerecke <killertofu@gmail.com>
Date: Wed, 18 Jan 2017 09:00:10 -0800
Subject: [PATCH] tests: Fix compilation under ABI 25 and greater

diff --git a/test/fake-symbols.c b/test/fake-symbols.c
index 6f2c10a..e649fb9 100644
--- a/test/fake-symbols.c
+++ b/test/fake-symbols.c
@@ -493,6 +493,7 @@ void TimerFree(OsTimerPtr timer)
 {
 }
 
+#if GET_ABI_MAJOR(ABI_XINPUT_VERSION) < 24
 int
 xf86BlockSIGIO (void)
 {
@@ -503,6 +504,15 @@ void
 xf86UnblockSIGIO (int wasset)
 {
 }
+#else
+void input_lock (void)
+{
+}
+
+void input_unlock (void)
+{
+}
+#endif
 
 /* This is not the same as the X server one, but it'll do for the tests */
 #if GET_ABI_MAJOR(ABI_XINPUT_VERSION) >= 14
-- 
2.11.1