add SQLite3MultipleCiphers lib support

[shamork]

SQLite3MultipleCiphers
https://github.com/utelle/SQLite3MultipleCiphers/

I've list steps to to use SQLite3MultipleCiphers with SQLitePCL.raw in https://github.com/shamork/SQLitePCLRaw.multipleciphers.

But I think I do not understand the this project structure enough to make a PR.

[ericsink]

Yeah, adding providers and a bundle is not trivial.

One question I have is whether I would even want to accept responsibility for maintaining support for SQLite3MultipleCiphers. I already maintain e_sqlcipher, the hassle is high enough that very often I wish I did not. :-)