Allow skipping the automatic sync on login/registration

This removes the currently unused "limit" parameter from
client:login_with_password() and client:register_with_password(), and adds a
new "no_sync" parameter. When the flag is set, the call to client:_sync() is
skipped. This can be useful for small scripts which do not need to do a sync
after login, yet they would rather user the higher level "matrix.client"
instead of the low level "matrix.api". For example, a simple script to send
a message to an already-known room given its ID could skip the sync in order
to be faster, without needing to revert to using "matrix.api".

matrix/client.lua

@@ -314,24 +314,26 @@ function Client:__tostring()
    return self.__name .. "{" .. self._api.base_url .. "}"
 end
 
-function Client:register_with_password(username, password, limit)
+function Client:register_with_password(username, password, no_sync)
    return self:_logged_in(self._api:register("m.login.password",
-      { user = username, password = password }), limit)
+      { user = username, password = password }), no_sync)
 end
 
-function Client:login_with_password(username, password, limit)
+function Client:login_with_password(username, password, no_sync)
    return self:_logged_in(self._api:login("m.login.password",
-      { user = username, password = password }), limit)
+      { user = username, password = password }), no_sync)
 end
 
-function Client:_logged_in(response, limit)
+function Client:_logged_in(response, no_sync)
    self._log("logged-in: %s", response.user_id)
    self.user_id    = response.user_id
    self.homeserver = response.home_server
    self.token      = response.access_token
    self._api.token = response.access_token
    self:fire("logged-in")
-   self:_sync()
+   if not no_sync then
+      self:_sync()
+   end
    return self.token
 end