btrace: Enable auxiliary instructions in record function-call-history.

Print the auxiliary data when a btrace_insn of type BTRACE_INSN_AUX
is encountered in the function-call-history.  Printing is
active by default, it can be silenced with the /a modifier.

This patch is in preparation for the new ptwrite feature, which is based on
auxiliary instructions.

Approved-By: Markus Metzger <markus.t.metzger@intel.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>