Add build option V7_NO_COMPILER

Which disables tokenizer, parser, AST, and compiler. On ESP8266, it
frees 21K of ROM.

PUBLISHED_FROM=ff4c53ace6b9056c595b9e12ef3453330d659775

docs/design-concept/event-handler.md

@@ -3,8 +3,8 @@ title: Event handler function
 ---
 
 Each connection has an event handler function associated with it. That function
-must be implemented by user. Event handler is the key element of the Mongoose
-application, since it defines application's behavior. This is how an event
+must be implemented by the user. Event handler is the key element of the Mongoose
+application, since it defines the application's behaviour. This is how an event
 handler function looks like:
 
 ```c
@@ -18,14 +18,14 @@ static void ev_handler(struct mg_connection *nc, int ev, void *ev_data) {
 
 - `struct mg_connection *nc`: Connection that has received an event.
 - `int ev`: Event number, defined in `mongoose.h`. For example, when data
-  arrives on inbound connection `ev` would be `MG_EV_RECV`.
+  arrives on an inbound connection, `ev` would be `MG_EV_RECV`.
 - `void *ev_data`: This pointer points to the event-specific data, and it has
-  different meaning for different events. For example, for `MG_EV_RECV` event,
+  a different meaning for different events. For example, for an `MG_EV_RECV` event,
   `ev_data` is an `int *` pointer, pointing to the number of bytes received
-  from the remote peer and saved into the receive IO buffer. Exact meaning of
+  from the remote peer and saved into the receive IO buffer. The exact meaning of
   `ev_data` is described for each event. Protocol-specific events usually have
   `ev_data` pointing to structures that hold protocol-specific information.
 
 NOTE: `struct mg_connection` has `void *user_data` which is a placeholder for
-an application-specific data. Mongoose does not use that pointer. Event handler
+application-specific data. Mongoose does not use that pointer. Event handler
 can store any kind of information there.