api_posting.bb is a new doco file that explains posting to the redmatrix from an external program by exampple of command line tool curl
main.bb is an updated version of the doco main site with a link to api_posting.bb
Added "if(!function_exists('xpost_to_html2bbcode'))"
This function name is also used by post to friendica plugin
Both functions seem to be identical. If you have both plugins installed
you get an error because of the identical function name
This will avoid the attempt to load the function a second time in case
it was already loaded by the post to friendica plugin
Merge pull request #566 from tonnerkiller/master

Posting by API and Wordpress plugin