Remove old Skylark Function hierarchy

Last step in refactoring of Skylark builtin functions.

--
MOS_MIGRATED_REVID=91796746
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java b/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
index bef2b09..ca73ea4 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.syntax;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Function;
 import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
@@ -134,7 +135,7 @@
    *         dictionary key) according to the rules of the Build language.
    */
   public static boolean isImmutable(Object o) {
-    if (o instanceof Map<?, ?> || o instanceof Function
+    if (o instanceof Map<?, ?> || o instanceof BaseFunction
         || o instanceof FilesetEntry || o instanceof GlobList<?>) {
       return false;
     } else if (o instanceof List<?>) {
@@ -282,7 +283,7 @@
       return "glob list";
     } else if (Map.class.isAssignableFrom(c)) {
       return "dict";
-    } else if (Function.class.isAssignableFrom(c)) {
+    } else if (BaseFunction.class.isAssignableFrom(c)) {
       return "function";
     } else if (c.equals(FilesetEntry.class)) {
       return "FilesetEntry";
@@ -371,8 +372,8 @@
       }
       buffer.append(")");
 
-    } else if (o instanceof Function) {
-      Function func = (Function) o;
+    } else if (o instanceof BaseFunction) {
+      BaseFunction func = (BaseFunction) o;
       buffer.append("<function " + func.getName() + ">");
 
     } else if (o instanceof FilesetEntry) {
@@ -504,8 +505,7 @@
    * Pretty-print values of 'o' separated by the separator.
    */
   public static String prettyPrintValues(String separator, Iterable<Object> o) {
-    return Joiner.on(separator).join(Iterables.transform(o,
-        new com.google.common.base.Function<Object, String>() {
+    return Joiner.on(separator).join(Iterables.transform(o, new Function<Object, String>() {
       @Override
       public String apply(Object input) {
         return prettyPrintValue(input);