Stéphane Seng authored Jul 14, 2019 and Christoph Reiter committed Jul 14, 2019

Prior to this, the only marshalling test cases available for GPtrArrays were
for GPtrArrays of strings.

This commit adds a marshalling test case for GPtrArrays of structures, with the
same objective than the gi_marshalling_tests_array_zero_terminated_return_struct() test case.
This also adds a similar marshalling test case for GArrays of structures, for
completeness.

This is a follow-up to GNOME/gjs#9 where a
regression has been detected with these types of GPtrArrays.