Revert "GHOST: GLX: Remove XInitThreads"

This reverts commit 7529690df3.

I tried to put manually add threading protection to GHOST around
Xlib calls but that did not fix the crashes. So reverting that
for now despite the performance implication on some system.

intern/ghost/intern/GHOST_SystemX11.cpp

@@ -125,6 +125,7 @@ GHOST_SystemX11(
       m_xkb_descr(NULL),
       m_start_time(0)
 {
+	XInitThreads();
 	m_display = XOpenDisplay(NULL);
 
 	if (!m_display) {