Mk/bsd.sites.mk: actualize SourceForge mirror list (more complete)

Test resolving and connectivity (proper HTTP response) for every
officially endorsed mirror from three different locations, using
this simple shell script:

set -e
for m in $(grep -v ^# /tmp/sf-mirrors); do
    host ${m}.dl.sourceforge.net
    curl --connect-timeout 30 -I http://${m}.dl.sourceforge.net/project/lazarus/Lazarus%20Zip%20_%20GZip/Lazarus%202.2.4/lazarus-2.2.4-0.tar.gz
done

With the following results over numerous runs:

GOX mirror (Itauna, Brazil) was inaccessible from everywhere;
additionally, AltusHost (Stockholm) and YeR (Azerbaijan) were
inaccessible from China, so do not offer them for the moment.

Please keep in mind that not all mirrors might be enabled at once
(mirrors sometimes are pulled from rotation), and not all mirrors
have all files -- in this case, it will respond with HTTP/1.1 302
Moved Temporarily redirect to another site.

Tested from: Guangzhou (China Mobile), New York City (NYI),

		Saint Petersburg (Rostelecom)