Minor change - MASTER_SITES no continuations

[Alistair Crooks <agc%pkgsrc.org@localhost>]

I'd like to apply the diff in:

https://www.netbsd.org/~agc/pkgsrc-master_sites-no-cont.diff

Simple changes to 352 pkgsrc entries so that the MASTER_SITES definitions use += for subsequent sites, and not continuation lines.

Makes it easier to grep for 'MASTER_SITES.*whatever"

Any objections?

Thanks,

Alistair