Update revisions.txt

Author: Federico Fissore

build/shared/revisions.txt

@@ -18,6 +18,7 @@ ARDUINO 1.6.6
 * Windows: IDE startup feels faster
 * Examples of libraries with a .development flag file in their root folder won't get marked as read-only. See #2619
 * Update notifications: when updates are available from either Library or Boards Managers, a popup will be shown
+* Introducing arduino-builder, a command line tool that properly calls gcc. Fixes lots of issues about buggy preprocessing.
 
 [libraries]