Turning stack_core into a class to make it compatible with adbs.

This includes the fairly large change of refactoring stack_core.py into
a class so that its behavior is compatible with adbs.  Additionally, if
the ABI line does not come before lines that require it to determine
proper widths (registers, stack), then it will assume that the ABI is
32 bit and not 64.

Change-Id: I6ad84a55337d86d25f7f8197048dc93868b0a01a

scripts/stack

@@ -69,7 +69,6 @@ def main():
   lines = f.readlines()
   f.close()
 
-  print "Reading symbols from", symbol.SYMBOLS_DIR
   stack_core.ConvertTrace(lines)
 
 if __name__ == "__main__":