Call XInitThreads early enough

We need to call XInitThreads before anyone tries XOpenDisplay or
something, and XInitThreads itself is not re-entrant, so call it before
we start LibVLC. This only "fixes" Xlib with VLC. Other LibVLC users
need to do something similar themselves. LibVLC cannot do it. Other
application may have already connected to X before it starts LibVLC.

bin/vlc.c

@@ -33,7 +33,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <locale.h>
-
+#ifdef HAVE_X11_XLIB_H
+# include <X11/Xlib.h>
+#endif
 
 /* Explicit HACK */
 extern void LocaleFree (const char *);
@@ -82,6 +84,15 @@ int main( int i_argc, const char *ppsz_argv[] )
 #   endif
 #endif
 
+#ifdef HAVE_X11_XLIB_H
+    /* Initialize Xlib thread support. */
+    if (!XInitThreads ())
+    {
+        fputs ("VLC requires a thread-safe Xlib. Sorry.\n", stderr);
+        return 1;
+    }
+#endif
+
     /* Synchronously intercepted POSIX signals.
      *
      * In a threaded program such as VLC, the only sane way to handle signals

configure.ac

@@ -3964,6 +3964,9 @@ AC_ARG_ENABLE(x11,
 
 CPPFLAGS="${CPPFLAGS_save} ${X_CFLAGS}"
 AC_CHECK_HEADERS(X11/Xlib.h, [
+  VLC_ADD_CPPFLAGS([vlc], [${X_CFLAGS}])
+  VLC_ADD_LIBS([vlc], [${X_LIBS} ${X_PRE_LIBS} -lX11])
+
   VLC_ADD_PLUGIN([screen])
   VLC_ADD_CPPFLAGS([screen],[${X_CFLAGS}])
   VLC_ADD_LIBS([screen],[${X_LIBS} ${X_PRE_LIBS} -lX11])