On SIM destruction free associated CCBs, preallocated inside xpt_get_ccb().
Before this change they were just leaked.  Fortunately USB sticks now use
only one CCB, and so leak was only 2KB per detach, while other bigger SIMs
with much more allocated CCBs are rarely detached.

MFC after:	2 weeks
Similar to r239870 and r239872, teach the other binutils tools about the
DW_FORM_flag_present dwarf attribute, so they do not print errors or
warnings on files that contain it.  (This attribute can be emitted by
newer versions of clang and gcc.)

MFC after:	1 week