add links to the nan guard mode and nan tutorials

doc/library/compile/index.txt

@@ -20,6 +20,7 @@
     mode
     debugmode
     profilemode
+    nanguardmode
 
 
 

doc/tutorial/index.txt

@@ -41,6 +41,7 @@ you out.
     aliasing
     shape_info
     debug_faq
+    nan_tutorial
     profiling
     extending_theano
     extending_theano_c