feat(client): expose http09 and http1 options on client::conn::Builder (#2611)

These options are currently available on the high-level builder only.

Along the way, rename the setters to follow the public API conventions
and add docs.

Closes #2461

src/ffi/client.rs

@@ -107,7 +107,7 @@ ffi_fn! {
     /// Creates a new set of HTTP clientconn options to be used in a handshake.
     fn hyper_clientconn_options_new() -> *mut hyper_clientconn_options {
         let mut builder = conn::Builder::new();
-        builder.h1_preserve_header_case(true);
+        builder.http1_preserve_header_case(true);
 
         Box::into_raw(Box::new(hyper_clientconn_options {
             builder,