Disable all features by default

Force callers to specifically enable required features before
running Prolog that needs to do file IO (e.g. pl2am or am2j) or
observe runtime statistics (consult in cafeteria).

Change-Id: Ifa24702806c7bf3425a0f5b497bf2c84f874d61f

src/compiler/Compiler.java

diff --git a/src/compiler/Compiler.java b/src/compiler/Compiler.java
index 5820745..1912022 100644
--- a/src/compiler/Compiler.java
+++ b/src/compiler/Compiler.java
@@ -99,6 +99,7 @@
     /** Initialize a new compiler instance. */
     public Compiler() {
       pcl = new BufferingPrologControl();
+      pcl.setEnabled(EnumSet.allOf(Prolog.Feature.class), true);
       pcl.setPrologClassLoader(new PrologClassLoader(Compiler.class.getClassLoader()));
       options = EnumSet.noneOf(Option.class);
       enableDefaultOptions();

src/lang/Prolog.java

diff --git a/src/lang/Prolog.java b/src/lang/Prolog.java
index 9b4237e..d64412f 100644
--- a/src/lang/Prolog.java
+++ b/src/lang/Prolog.java
@@ -106,7 +106,7 @@
       /** Track the running time of evaluations */
       STATISTICS_RUNTIME;
     }
-    protected final EnumSet<Feature> features = EnumSet.allOf(Feature.class);
+    protected final EnumSet<Feature> features = EnumSet.noneOf(Feature.class);
 
     Prolog(PrologControl c) {
       control = c;

src/repl/PrologMain.java

diff --git a/src/repl/PrologMain.java b/src/repl/PrologMain.java
index cb1f0f8..4a83588 100644
--- a/src/repl/PrologMain.java
+++ b/src/repl/PrologMain.java
@@ -13,6 +13,7 @@
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 import java.io.PushbackReader;
+import java.util.EnumSet;
 import java.util.StringTokenizer;
 /**
  * Prolog Cafe launcher.
@@ -63,6 +64,7 @@
 	    }
 
 	    p = new BlockingPrologControl();
+	    p.setEnabled(EnumSet.allOf(Prolog.Feature.class), true);
 		p.getStreamManager().put(
 			SymbolTerm.intern("user_input"),
 			new JavaObjectTerm(new PushbackReader(new BufferedReader(