Update revision log

Author: sandeepmistry

build/shared/revisions.txt

@@ -4,6 +4,8 @@ ARDUINO 1.6.12
 * Refactor Editor code, solving some long standing bugs and cleaning up everything. Thanks @matthijskooijman
 * Add initial Cloud API integration. When plugging a new board, if an additional core is needed, the user will be prompted to install it
 
+[core]
+* avr: Add support for internal 2.56V and 2.56V ext. cap analog references on the ATtiny25/45/85. Thanks @mischnic
 
 ARDUINO 1.6.11 - 2016.08.17