More exports cleanup (#522)

* annotate `SecureProtocol.Secio` as deprecated

* dont export varint

* add `errors` to exports - convenient error utils

libp2p.nim

@@ -17,7 +17,7 @@ import
           transports/transport,
           transports/tcptransport,
           protocols/secure/noise,
-          varint,
+          errors,
           switch,
           peerid,
           peerinfo,
@@ -27,7 +27,7 @@ import
 import bearssl
 
 export
-  minprotobuf, varint,switch, peerid, peerinfo,
+  minprotobuf, switch, peerid, peerinfo,
   connection, multiaddress, crypto, lpstream,
   bufferstream, bearssl, muxer, mplex, transport,
-  tcptransport, noise
+  tcptransport, noise, errors

libp2p/standard_setup.nim

@@ -9,7 +9,7 @@ import connmanager
 type
   SecureProtocol* {.pure.} = enum
     Noise,
-    Secio # deprecated
+    Secio {.deprecated.}
 
 proc newStandardSwitch*(privKey = none(PrivateKey),
                         address = MultiAddress.init("/ip4/127.0.0.1/tcp/0").tryGet(),