Expose libraries loaded via ctypes() globally.

Index: pyglet/lib.py
--- pyglet/lib.py.orig
+++ pyglet/lib.py
@@ -145,7 +145,7 @@ class LibraryLoader(object):
         platform_names.extend(names)
         for name in platform_names:
             try:
-                lib = ctypes.cdll.LoadLibrary(name)
+                lib = ctypes.CDLL(name, ctypes.RTLD_GLOBAL)
                 if _debug_lib:
                     print(name)
                 if _debug_trace:
@@ -155,7 +155,7 @@ class LibraryLoader(object):
                 path = self.find_library(name)
                 if path:
                     try:
-                        lib = ctypes.cdll.LoadLibrary(path)
+                        lib = ctypes.CDLL(path, ctypes.RTLD_GLOBAL)
                         if _debug_lib:
                             print(path)
                         if _debug_trace:
@@ -274,7 +274,7 @@ class MachOLibraryLoader(LibraryLoader):
     def load_framework(self, path):
         realpath = self.find_framework(path)
         if realpath:
-            lib = ctypes.cdll.LoadLibrary(realpath)
+            lib = ctypes.CDLL(realpath, ctypes.RTLD_GLOBAL)
             if _debug_lib:
                 print(realpath)
             if _debug_trace: