Upgrade rust/crates/protobuf to 2.17.0

* Android.bp was regenerated. New rustc warnings were found.
* Keep local change in src/lib.rs to include out/version.rs.
* Update out/version.rs to the new version.

Change-Id: I9c2f7d412dcd42fe3769505629e05ab949300fe6
Test: make
diff --git a/src/reflect/optional.rs b/src/reflect/optional.rs
index 4d33752..ba6cbaf 100644
--- a/src/reflect/optional.rs
+++ b/src/reflect/optional.rs
@@ -2,7 +2,7 @@
 
 use super::value::ProtobufValue;
 
-use singular::*;
+use crate::singular::*;
 
 pub trait ReflectOptional: 'static {
     fn to_option(&self) -> Option<&ProtobufValue>;