Revision 415842

Extract the larger bsd.port.mk targets into separate scripts.

Refactor all the fetch code so that there are not 6 slightly different
versions of it but one that does it all.

The targets that have been extracted are:
- check-vulnerable
- do-fetch
- fetch-list
- fetch-url-list-int
- fetch-urlall-list
- checksum.
- makesum.
- check-checksum-algorithms

Run the fetch code directly from make makesum instead of calling make
fetch, this is because some port change the options with OPTIONS_*_FORCE
when make(makesum) to be able to add all distfiles in one go, which was
a nice, non working, idea.

PR:		208916
Submitted by:	mat
Exp-run by:	antoine
With hat:	portmgr
Sponsored by:	Absolight
Differential Revision:	https://reviews.freebsd.org/D5997