CC2420X driver fixes

pull request 173: fixed a critical race condition that caused the driver
to hang under high loads, restructured code to eliminate long atomic
sections
Add .gitignore rules for after tools/Bootstrap invocation
Add .gitignore rules for after tools/configure invocation
Add .gitignore rules for after make -C tools invokation
Merge pull request #175 from ppannuto/gitignore

Add .gitignore rules for built items in the tools/ directory
Merge remote-tracking branch 'lab11/master'