Ports with LOCAL/xxx as a MASTER_SITE

[Yuri]

I came across a few ports like this. Most recently www/npm. It usually 
turns out that some slightly modified version of sources is kept there @ 
LOCAL/xxxx.

Why not just have the patches under files/ do the modification, so that 
it is public and reproducible? There are also GitHub and Bitbucket, 
among other places, to keep sources. There should be no need to allow 
LOCAL/xxx as a MASTER_SITE nowadays.

I suggest to abolish this practice. Begin with adding a warning to the 
port infrastructure when LOCAL/xxx is specified.

(It makes it more difficult to suggest the patch to such port, because 
outsiders should first "reverse-engineer" the patches, which should have 
been there in files/ in the first place.)

Yuri