Basic APIs and tests for extracting attachments

1. Added API for extracting attachment properties and data.
  * Expanded the embedder test to cover all the new APIs.

Bug=pdfium:174

Change-Id: I09bffd412410e9aea45faca442d2b72eefafef4e
Reviewed-on: https://pdfium-review.googlesource.com/7790
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
diff --git a/public/fpdfview.h b/public/fpdfview.h
index 95900f3..55897eb 100644
--- a/public/fpdfview.h
+++ b/public/fpdfview.h
@@ -20,9 +20,22 @@
 #define PDF_USE_XFA
 #endif  // PDF_ENABLE_XFA
 
+// PDF object types
+#define FPDF_OBJECT_UNKNOWN 0
+#define FPDF_OBJECT_BOOLEAN 1
+#define FPDF_OBJECT_NUMBER 2
+#define FPDF_OBJECT_STRING 3
+#define FPDF_OBJECT_NAME 4
+#define FPDF_OBJECT_ARRAY 5
+#define FPDF_OBJECT_DICTIONARY 6
+#define FPDF_OBJECT_STREAM 7
+#define FPDF_OBJECT_NULLOBJ 8
+#define FPDF_OBJECT_REFERENCE 9
+
 // PDF types
 typedef void* FPDF_ACTION;
 typedef void* FPDF_ANNOTATION;
+typedef void* FPDF_ATTACHMENT;
 typedef void* FPDF_BITMAP;
 typedef void* FPDF_BOOKMARK;
 typedef void* FPDF_CLIPPATH;