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/DotExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/DotExpression.java
index e5b06a9..bb0e8ed 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/DotExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/DotExpression.java
@@ -27,9 +27,9 @@
 
   private final Expression obj;
 
-  private final Ident field;
+  private final Identifier field;
 
-  public DotExpression(Expression obj, Ident field) {
+  public DotExpression(Expression obj, Identifier field) {
     this.obj = obj;
     this.field = field;
   }
@@ -38,7 +38,7 @@
     return obj;
   }
 
-  public Ident getField() {
+  public Identifier getField() {
     return field;
   }