v1.3.19 - add timeout for complete header read

In order to fight the slow http header Denial of Service attack
there is now a parameter to control the maximum amount of time
AllegroServe will spend reading the headers of a request

Are there user-visible changes that require documentation?  yes
 I'll file a documentation bug with the details about the new
 variable and method

Change-Id: Ib79e7b002877b8918ac8e2b031a4ac61cc092451