Prepare for release 2.2.1

* Update NEWS
* Update configure.ac

Fix clean files in docu build

Release avr-libc 2.1.0

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-2_1_0-release@2557 1084037a-409f-4a99-8160-1a4b3577d4c1

Release for version 2.0.0.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-2_0_0-release@2516 1084037a-409f-4a99-8160-1a4b3577d4c1

Release 1.8.0 tag.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-1_8_0-release/avr-libc@2273 1084037a-409f-4a99-8160-1a4b3577d4c1

This commit was manufactured by cvs2svn to create tag 'avr-

libc-1_6_8-release'.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-1_6_8-release/avr-libc@2097 1084037a-409f-4a99-8160-1a4b3577d4c1

This commit was manufactured by cvs2svn to create tag 'WinAVR-20100110'.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/WinAVR-20100110/avr-libc@2091 1084037a-409f-4a99-8160-1a4b3577d4c1

This commit was manufactured by cvs2svn to create tag 'avr-

libc-1_6_7-release'.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-1_6_7-release/avr-libc@2011 1084037a-409f-4a99-8160-1a4b3577d4c1

This commit was manufactured by cvs2svn to create tag 'avr-

libc-1_6_6-release'.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-1_6_6-release/avr-libc@1929 1084037a-409f-4a99-8160-1a4b3577d4c1

This commit was manufactured by cvs2svn to create tag 'avr-

libc-1_6_5-release'.

git-svn-id: https://svn.savannah.nongnu.org/svn/avr-libc/tags/avr-libc-1_6_5-release/avr-libc@1920 1084037a-409f-4a99-8160-1a4b3577d4c1