Only activate menu items if the mouse releases in them - fixes #4863

[samdroid-apps]

Ticket URL http://bugs.sugarlabs.org/ticket/4863

@quozl wrote a very good ticket which serves as a good description:

The industry convention for mouse driven menu options is for them to be activated when two conditions are met:

• a button down event occurs with the pointer inside the option, and;
• a button up event occurs with the pointer inside the option.

The latter condition is not being checked in the Sugar menus.

Reproducer: right-click on the buddy menu, put the pointer over the My Settings option, press down on the button, move the pointer out of the menu, release the button.

Expected result: menu is dismissed.

Observed result: menu is dismissed, and the My Settings option is activated.

[godiard]

Excellent. Next time, please include the explanation in the patch header, that is what will be visible on the git log. (You put the link to the ticket that is ok, but then you need look for the information in the ticket.)