Make libxcb compile with gcc 4.9.

var/spack/repos/builtin/packages/libxcb/package.py

 from spack import *
 
 class Libxcb(Package):
-    """The X protocol C-language Binding (XCB) is a replacement 
-    for Xlib featuring a small footprint, latency hiding, direct 
-    access to the protocol, improved threading support, and 
+    """The X protocol C-language Binding (XCB) is a replacement
+    for Xlib featuring a small footprint, latency hiding, direct
+    access to the protocol, improved threading support, and
     extensibility."""
 
     homepage = "http://xcb.freedesktop.org/"
@@ -14,6 +14,10 @@ class Libxcb(Package):
     depends_on("python")
     depends_on("xcb-proto")
 
+    def patch(self):
+        filter_file('typedef struct xcb_auth_info_t {', 'typedef struct {', 'src/xcb.h')
+
+
     def install(self, spec, prefix):
         configure("--prefix=%s" % prefix)