Replaced the 'C' version of system_tick() with the assembly version.

git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2346 1084037a-409f-4a99-8160-1a4b3577d4c1
Corrected Filea.am to include 'solar_noon()'

git-svn-id: http://svn.savannah.nongnu.org/svn/avr-libc/trunk@2347 1084037a-409f-4a99-8160-1a4b3577d4c1