Nuke xpi-* ports

Legacy extensions aren't supported by Firefox anymore. Very few were
maintained up until last year when AMO stopped hosting files.

Remove unnecessary evals that do-fetch was using.

Turns out that env(1) knows how to parse a properly quoted string
using -S "string", it makes the double eval used for the fetch
command to be unnecessary.

This is because running:
eval "foo $(escape $bar)"
is silly when this works:
foo $bar

So remove escaping and quoting, and sillyness.

PR:		210198
Submitted by:	mat
Exp-run by:	antoine
Sponsored by:	The FreeBSD Foundation, Absolight
Differential Revision:	https://reviews.freebsd.org/D6779

Fix build.

Remove indefinite articles and trailing periods from COMMENT, plus
minor COMMENT typos and surrounding whitespace fixes. A few Makefiles
where not included as they contain Latin-1 characters that break
the Phabricator workflow. Category W.

CR:		D510
Approved by:	portmgr (bapt)

- Stage support

Add NO_STAGE all over the place in preparation for the staging support (cat:
www)

- Reassign ports from avl@ back to pool at his request.

Submitted by:	avl via IM
Approved by:	avl via IM

- Get Rid MD5 support

Change MAINTAINER on my ports to my FreeBSD email address

Approved by:    tabthorpe (mentor)

- Update to 2.0.2

PR:             131760
Submitted by:   Alexander Logvinov <ports@logvinov.com> (maintainer)

Adds a splash screen to most Mozilla and Mozilla Based products.
Supports sound, opacity, CSS customization, custom images, and much more.
You can add {appVersion}, {buildID} and {userAgent} to the loading text and
it will be filled in for you.

WWW: http://www.mrtech.com/extensions/

PR:             ports/128111
Submitted by:   Alexander Logvinov <ports at logvinov.com>