maint: avoid further typedef accidents

maint: avoid further typedef accidents

To make it easier to forbid future attempts at a confusing typedef
name ending in Ptr that isn't actually a pointer, insist that we
follow our preferred style of 'typedef foo *fooPtr'.

* cfg.mk (sc_forbid_const_pointer_typedef): Enforce consistent
style, to prevent issue fixed in previous storage patch.
* src/conf/capabilities.h (virCapsPtr): Fix offender.
* src/security/security_stack.c (virSecurityStackItemPtr):
Likewise.
* tests/qemucapabilitiestest.c (testQemuDataPtr): Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>