Provide sr_parse_coredump_maps even without unwinder

Consistent with the sr_parse_coredump stub function. (Implementation
note: the sr_parse_coredump wrapper was moved to core_unwind.c in order
not to have it duplicated three times.)

Related to #127.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Merge pull request #167 from abrt/gh127_report_maps_fix

Provide sr_parse_coredump_maps even without unwinder