testsuite: adapt g++.dg/ipa/pr83667.C for AIX

The current testsuite regex looks for THUNK0.  AIX generates THUNK..0.
This patch expands the regex to allow 0 or more dots between THUNK
and the 0.

gcc/testsuite/ChangeLog

2020-07-14  David Edelsohn  <dje.gcc@gmail.com>

	* g++.dg/ipa/pr83667.C: Allow 0 or more dots between THUNK and 0.