Show HN: Update of Emacs' calendar to enable changing number of months displayed

Got fed up with lack of way of changing the number of months displayed by Emacs' calendar, and after a fruitless web search for a solution, wrote the fix myself. So, I decided to share.

FYI:

* Adds the new function 'calendar-set-num-months' to the built-in emacs calendar, which changes the number of months displayed in the calendar

* Number of months defaults to 3 (as per original calendar) but can be set to e.g. 6 or 12 months using 'calendar-set-num-months'.

* Alternatively, you can change the default number of months by editing the value of 'calendar-num-months' in this file.