reporter-priv: Passing a string parm by reference

reporter-priv: Passing a string parm by reference

While looking at something else, I noticed the
maybe_report_data_members_replaced_by_anon_dm function was passing a
string parameter by value.  Pass this by reference.

	* src/abg-reporter-priv.h
	(maybe_report_data_members_replaced_by_anon_dm): Pass the string parm by ...
	* src/abg-reporter-priv.cc
	(maybe_report_data_members_replaced_by_anon_dm): ... reference.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>