gdb/progspace: rename progspace::so_list, make private

Rename the field to m_solib_list, make it private.  Update users to go
through the accessor.

Change-Id: Id720c3a0b1781f4acf31e0dc626f1bd23ed8b39a
Reviewed-By: Guinevere Larsen <guinevere@redhat.com>
2 files changed