pull in DerelictGL3 and load it

.gitmodules

@@ -4,3 +4,12 @@
 [submodule "libs/glcxx"]
 	path = libs/glcxx
 	url = git://github.com/holtrop/glcxx.git
+[submodule "libs/DerelictGL3"]
+	path = libs/DerelictGL3
+	url = git://github.com/DerelictOrg/DerelictGL3
+[submodule "libs/DerelictGLFW3"]
+	path = libs/DerelictGLFW3
+	url = git://github.com/DerelictOrg/DerelictGLFW3
+[submodule "libs/DerelictUtil"]
+	path = libs/DerelictUtil
+	url = git://github.com/DerelictOrg/DerelictUtil