Move CPDFSDK_Annot, CPDFSDK_BAAnnot and CPDFSDK_DateTime to their own files.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 3ead13c8498f89b6385b49d94b01c6a0df96e960..16076288a03b4097e129da282ade0273a2c8d9e1 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -64,6 +64,9 @@ static_library("pdfium") {
   sources = [
     "fpdfsdk/cfx_systemhandler.cpp",
     "fpdfsdk/cfx_systemhandler.h",
+    "fpdfsdk/cpdfsdk_annot.cpp",
+    "fpdfsdk/cpdfsdk_baannot.cpp",
+    "fpdfsdk/cpdfsdk_datetime.cpp",
     "fpdfsdk/fpdf_dataavail.cpp",
     "fpdfsdk/fpdf_ext.cpp",
     "fpdfsdk/fpdf_flatten.cpp",
@@ -81,13 +84,14 @@ static_library("pdfium") {
     "fpdfsdk/fpdfview.cpp",
     "fpdfsdk/fsdk_actionhandler.cpp",
     "fpdfsdk/fsdk_annothandler.cpp",
-    "fpdfsdk/fsdk_baseannot.cpp",
     "fpdfsdk/fsdk_baseform.cpp",
     "fpdfsdk/fsdk_mgr.cpp",
     "fpdfsdk/fsdk_pauseadapter.cpp",
+    "fpdfsdk/include/cpdfsdk_annot.h",
+    "fpdfsdk/include/cpdfsdk_baannot.h",
+    "fpdfsdk/include/cpdfsdk_datetime.h",
     "fpdfsdk/include/fsdk_actionhandler.h",
     "fpdfsdk/include/fsdk_annothandler.h",
-    "fpdfsdk/include/fsdk_baseannot.h",
     "fpdfsdk/include/fsdk_baseform.h",
     "fpdfsdk/include/fsdk_pauseadapter.h",
     "public/fpdf_dataavail.h",