Add crypto libraries

Add C++ versions of the BoringSSL crypto functions we need (copied
from keystore) and create Rust wrappers for them.

Test: atest keystore2_test
Change-Id: I21ff8630df26ca73ae36395c5303270e96a6deb6
diff --git a/keystore2/src/lib.rs b/keystore2/src/lib.rs
index 067399e..3e13c5f 100644
--- a/keystore2/src/lib.rs
+++ b/keystore2/src/lib.rs
@@ -14,6 +14,7 @@
 
 //! This crate implements the Android Keystore 2.0 service.
 
+mod crypto;
 pub mod database;
 pub mod error;
 pub mod globals;