pull in DerelictGL3 and load it

Rsconscript

@@ -6,9 +6,9 @@ end
 
 build do
   main_env = Rscons::Environment.new do |env|
-    env["sources"] = glob("src/**/*.{c,d}")
+    env["sources"] = glob("src/**/*.{c,d}", "libs/Derelict*/**/*.d")
     env["CCFLAGS"] += %w[-Wall]
-    env["D_IMPORT_PATH"] += glob("src/**")
+    env["D_IMPORT_PATH"] += glob("src/**", "libs/Derelict*/source")
     env["DFLAGS"] += %w[-Wall]
     env["LIBS"] += %w[X11 GLX]
     env.Program("jes", "${sources}")