crc_changed: eliminate copying of shared_ptr values

crc_changed: eliminate copying of shared_ptr values

As pointed out in a review of similar code, it is possible to avoid
copying a couple of shared pointers in this function, by taking
references instead.

This commit also splits declarations to one per line and removes the
unnecessary parentheses around the return expression.

	* src/abg-comp-filter.cc (crc_changed): Take references to
	avoid std::shared_ptr copying. Split declarations into one per
	line. Remove unnecessary return expression parentheses.

Reviewed-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Giuliano Procida <gprocida@google.com>