Notifies the application about a signed message.
The class fires this event when it identifies a signed message to allow the application to prepare the component for verification.
Use the KeyIDs parameter to identify keys used that were used to sign the message, and make sure they are available in the VerifyingKeys list.
SignatureType indicates the signature type:
|pstNormal||0||A traditional signature, compatible (algorithm permitting) with PGP 2.6.x|
|pstOnePass||1||A newer one-pass signature|
|pstDetached||2||A detached signature, i.e., a signature contained in a separate file from the data it covers|
|pstCleartext||3||A signature made over textual data and appended to it|