gdb/solib: make solib_ops::solib_create_inferior_hook optional

The solib-target implementation of solib_create_inferior_hook is empty.
Make that method / function pointer optional.

Change-Id: Ie27b8d2c4fc6df74069ac8f88fbe69cf88a6662d
Reviewed-By: Guinevere Larsen <guinevere@redhat.com>
2 files changed