remove avr-rtems support

contrib/ChangeLog:

2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* config-list.mk: Stop testing avr-rtems.

libgcc/ChangeLog:

2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* config.host: Remove support for avr-rtems.
	* config/avr/t-rtems: Remove.

ChangeLog:

2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* configure: Regenerate.
	* configure.ac: Remove support for avr-rtems.

gcc/ChangeLog:

2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* config.gcc: Remove support for avr-rtems.
	* config/avr/gen-avr-mmcu-specs.c: Likewise.
	* config/avr/rtems.h: Remove.
	* config/avr/t-rtems: Remove.

contrib/header-tools/ChangeLog:

2016-06-21  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* README: Remove references to avr-rtems.
	* reduce-headers: Likewise.

From-SVN: r237665