Add propane and initial scene grammar

Rsconscript

@@ -6,7 +6,16 @@ fart_env = env "fart" do |env|
   env["DFLAGS"] += %w[-Werror -O2]
   env["D_IMPORT_PATH"] += %w[src]
 
-  env["sources"] = glob("src/**/*.d")
+  env.Command("^/src/sceneparser.d", "src/sceneparser.propane",
+              "CMD" => %w[./propane ${_SOURCES} ${_TARGET}],
+              "CMD_DESC" => "Generating scene parser")
+  env.add_build_hook do |builder|
+    if builder.sources.first =~ /sceneparser\.d/
+      builder.vars["DFLAGS"] -= %w[-Werror]
+    end
+  end
+
+  env["sources"] = glob("src/**/*.d") + ["^/src/sceneparser.d"]
   env.Program("fart", "${sources}")
 end