syscall: introduce Pointer type and use it instead of uintptr
Some syscall structures used by crypto/x509 have uintptr
fields that store pointers. These pointers are set with
a pointer to another Go structure. But the pointers are
not visible by garbage collector, and GC does not update
the fields after they were set. So when structure with
invalid uintptr pointers passed to Windows, we get
memory corruption.
This CL introduces CertInfo, CertTrustListInfo and
CertRevocationCrlInfo types. It uses pointers to new types
instead of uintptr in CertContext, CertSimpleChain and
CertRevocationInfo.
CertRevocationInfo, CertChainPolicyPara and
CertChainPolicyStatus types have uintptr field that can
be pointer to many different things (according to Windows
API). So this CL introduces Pointer type to be used for
those cases.