Prepare for release 1.8.1.



git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2447 1084037a-409f-4a99-8160-1a4b3577d4c1
Trunk is post-release now (as release has been tagged).



git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2449 1084037a-409f-4a99-8160-1a4b3577d4c1
Fix broken revision_suffix macro.



git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2450 1084037a-409f-4a99-8160-1a4b3577d4c1