Merge to XFA: Add type cast definitions for CPDF_Name.

This Cl adds ToName, CPDF_Object::AsName and CPDF_Object::IsName and
updates the src to use them as needed.

BUG=pdfium:201
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1417823005 .

(cherry picked from commit 1c77edb7b34e03787605b7965784cea38ef9f1d7)

Review URL: https://codereview.chromium.org/1417033004 .
22 files changed