Now that we have www/webkit in ports, split it into MULTI_PACKAGES :
-main has the common infrastructure files (and the binary), -gecko provides
gecko engine support, -webkit provides webkit engine support.
To ease updates, -gecko has the same pkgname as previous package. -webkit
support is still a bit experimental, and provided for webdevelopers who
want to write and test cross-engine websites.
With help and ok ajacoutot@
