ART: Fix variable formatting and CodeLayout's multiple visits

The CodeLayout pass visits multiple times the same BasicBlock. This patch
  fixes that issue to reduce its overhead.

The patch also fixes cUnit to c_unit in the bb_optimization files.

Change-Id: I76afa73dc79b9ee9993223c066a974ca81adf203
Signed-off-by: Jean Christophe Beyler <jean.christophe.beyler@intel.com>