CERT_INFO.rgExtension metadata isn't consistent with docs

[AArnott]

The metadata describes CERT_INFO.rgExtension as a pointer to a CERT_EXTENSION struct. But the documentation indicates the field is "An array of pointers to CERT_EXTENSION structures", suggesting this last field is actually an inline array of pointers instead of just one pointer.

[riverar]

Perhaps we should add another field to NativeArrayInfoAttribute to track which struct field contains length information (e.g. CountFieldName)