trywhy3: add a patch to switch to the python input

TODO: make this a configurable option

src/trywhy3/try-python.patch

+diff --git a/Makefile.in b/Makefile.in
+index 6f980b1cf..c55207be1 100644
+--- a/Makefile.in
++++ b/Makefile.in
+@@ -1503,7 +1503,7 @@ ALTERGOMODS=util/config util/version util/emap util/myUnix util/myDynlink \
+ 	main/frontend
+ 
+ ALTERGOCMO=$(addprefix $(ALTERGODIR)/src/, $(addsuffix .cmo,$(ALTERGOMODS)))
+-TRYWHY3CMO=lib/why3/why3.cma
++TRYWHY3CMO=lib/why3/why3.cma lib/plugins/python.cmo
+ TRYWHY3FILES=trywhy3.js trywhy3.html trywhy3.css \
+ 	README examples/ \
+ 	trywhy3_custom.css gen_index.sh fontawesome/css/font-awesome.min.css \
+@@ -1511,6 +1511,7 @@ TRYWHY3FILES=trywhy3.js trywhy3.html trywhy3.css \
+ 	fontawesome/fonts/fontawesome-webfont.woff fontawesome/fonts/fontawesome-webfont.eot \
+ 	fontawesome/fonts/fontawesome-webfont.ttf  fontawesome/fonts/fontawesome-webfont.woff2 \
+ 	ace-builds/src-min-noconflict/ace.js ace-builds/src-min-noconflict/mode-why3.js \
++	ace-builds/src-min-noconflict/mode-python.js \
+ 	ace-builds/src-min-noconflict/theme-chrome.js $(JS_MAPS)
+ 
+ trywhy3_package: trywhy3
+diff --git a/src/trywhy3/trywhy3.html b/src/trywhy3/trywhy3.html
+index b1f85157e..f19a32042 100644
+--- a/src/trywhy3/trywhy3.html
++++ b/src/trywhy3/trywhy3.html
+@@ -13,7 +13,7 @@
+     <script type="text/javascript">
+       var load_embedded_files = false;
+       var editor_theme = "ace/theme/chrome";
+-      var editor_mode = "ace/mode/why3";
++      var editor_mode = "ace/mode/python";
+       var task_viewer_mode = "ace/mode/why3";
+       var library_index = "examples/index.txt";
+     </script>
+diff --git a/src/trywhy3/why3_worker.ml b/src/trywhy3/why3_worker.ml
+index a1e17ac6f..8221c4ff8 100644
+--- a/src/trywhy3/why3_worker.ml
++++ b/src/trywhy3/why3_worker.ml
+@@ -24,7 +24,7 @@ let () = log_time ("Initialising why3 worker: start ")
+ 
+ (* Name of the pseudo file *)
+ 
+-let temp_file_name = "/trywhy3_input.mlw"
++let temp_file_name = "/trywhy3_input.py"
+ 
+ (* reads the config file *)
+ let config : Whyconf.config = Whyconf.read_config (Some why3_conf_file)