Reorganize the avr-binutils port to use the central binutils one
(as the various arm*binutils ports are doing, too).

Add a patch to recognize the "avrtiny" architecture MCUs (ATtiny10
et al.), extracted from the Atmel AVR Toolchain 3.4.5 (they still
didn't push it upstream, alas).
Add missing file in pkg-plist.
devel/linux-*-devtools: remove GMP

With GMP in linux_base-* remove its occurrence in the devtools port.

Spotted by:	antoine
Differential Revision:	https://reviews.freebsd.org/D1256
Approved by:	swills (mentor)