Always load avr-libc and related packages from server when making a release.

Atmel may update patches without changing the package name. We therefore always download the latest version.
New versions of avr-gcc and binutils
Various fixes for new package contents.

Packages downloaded from Atmel have new names and contents.
Define UMSEL0 and UMSEL1  in ATTiny2313a and 4313 headers.

The original patch did not change UMSEL to UMSEL0 and UMSEL1.