Renamed Ident to Identifier, added some helper methods and refactored two methods.

--
MOS_MIGRATED_REVID=98922811
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FunctionDefStatement.java b/src/main/java/com/google/devtools/build/lib/syntax/FunctionDefStatement.java
index dce9e9c..f9e26ed 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FunctionDefStatement.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FunctionDefStatement.java
@@ -24,11 +24,11 @@
  */
 public class FunctionDefStatement extends Statement {
 
-  private final Ident ident;
+  private final Identifier ident;
   private final FunctionSignature.WithValues<Expression, Expression> args;
   private final ImmutableList<Statement> statements;
 
-  public FunctionDefStatement(Ident ident,
+  public FunctionDefStatement(Identifier ident,
       FunctionSignature.WithValues<Expression, Expression> args,
       Collection<Statement> statements) {
     this.ident = ident;
@@ -59,7 +59,7 @@
     return "def " + ident + "(" + args + "):\n";
   }
 
-  public Ident getIdent() {
+  public Identifier getIdent() {
     return ident;
   }