'wr' open mode added

com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/ConnectionFunctions.java

@@ -345,7 +345,7 @@ public abstract class ConnectionFunctions {
             Casts casts = new Casts(TextConnection.class);
             CastsHelper.description(casts);
             casts.arg("text").allowNull().mustBe(stringValue());
-            CastsHelper.open(casts).mustBe(equalTo("").or(equalTo("r").or(equalTo("w").or(equalTo("a")))), RError.Message.UNSUPPORTED_MODE);
+            CastsHelper.open(casts).mustBe(equalTo("").or(equalTo("r").or(equalTo("w").or(equalTo("a").or(equalTo("wr"))))), RError.Message.UNSUPPORTED_MODE);
             casts.arg("env").mustNotBeNull(RError.Message.USE_NULL_ENV_DEFUNCT).mustBe(instanceOf(REnvironment.class));
             casts.arg("encoding").asIntegerVector().findFirst().mustNotBeNA();
         }

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/conn/ConnectionSupport.java

@@ -222,7 +222,7 @@ public class ConnectionSupport {
     enum AbstractOpenMode {
         Lazy(new String[]{""}, true, true, true),
         Read(new String[]{"r", "rt"}, true, true, false),
-        Write(new String[]{"w", "wt"}, true, false, true),
+        Write(new String[]{"w", "wt", "wr"}, true, false, true),
         Append(new String[]{"a", "at"}, true, false, true),
         ReadBinary(new String[]{"rb"}, false, true, false),
         WriteBinary(new String[]{"wb"}, false, false, true),