Add a test join between pgsql and r, and a test class

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/RTestSimple.java

+package com.oracle.truffle.r.test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import com.oracle.truffle.r.launcher.RscriptCommand;
+
+/**
+ * This class runs FastR on every R file it can find in given directories (it will search
+ * recursively).
+ */
+public final class RTestSimple {
+    public static final void main(String[] args) {
+        System.out.println("Testing: " + args[0]);
+        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        final String expected;
+        try {
+            expected = String.join("\n", Files.readAllLines(Paths.get(args[0].replaceFirst("\\.[Rr]$", ".out"))));
+            RscriptCommand.doMain(new String[]{"Rscript", args[0]}, null, System.in, new PrintStream(baos), System.err);
+            if (expected.equals(baos.toString()))
+                System.out.println("[SUCCESS]");
+            else {
+                System.out.println("[FAILED] Expected: ");
+                System.out.println(expected);
+                System.out.println("got: ");
+                System.out.println(baos.toString());
+            }
+        } catch (IOException e) {
+            System.err.println("[FAILED] Could not find expected output.");
+        }
+        System.out.flush();
+        System.err.flush();
+        try {
+            Thread.sleep(10);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+}

com.oracle.truffle.r.test/tests/PGSQL-R.R

+emp = new.tableRef("emp", "PostgreSQL", "postgre.config", "public")
+dept = data.frame(deptno = c(1, 2, 3), loc = c("NEW YORK", "MIAMI", "SAN FRANCISCO"))
+
+q = query.select(function (x) {
+             res = new.env()
+             res$ename = x$ename
+             res },
+    query.where(function (x) x$loc == "NEW YORK",
+    query.join(query.from(emp), dept, function (x,y) x$deptno == y$deptno)))
+results = query.force(q)
+print(results)

com.oracle.truffle.r.test/tests/PGSQL-R.out

+   ename
+1  CLARK
+2   KING
+3 MILLER
+