More IFX_ interface cleanup.

xfa.gyp

 {
   "variables": {
     "pdf_enable_v8%": 1,
   },
   "target_defaults": {
     "defines": [
       "PDF_ENABLE_XFA",
     ],
     'msvs_disabled_warnings': [
       4005, 4018, 4146, 4333, 4345, 4267,
@@ skipping 108 matching lines @@
         "xfa/fgas/layout/fgas_textbreak.h",
         "xfa/fgas/layout/fgas_unicode.cpp",
         "xfa/fgas/layout/fgas_unicode.h",
         "xfa/fgas/localization/fgas_datetime.cpp",
         "xfa/fgas/localization/fgas_datetime.h",
         "xfa/fgas/localization/fgas_locale.cpp",
         "xfa/fgas/localization/fgas_locale.h",
         "xfa/fgas/localization/fgas_localeimp.h",
         "xfa/fgas/localization/fgas_localemgr.cpp",
         "xfa/fgas/localization/fgas_localemgr.h",
+        "xfa/fgas/xml/fgas_sax.cpp",
         "xfa/fgas/xml/fgas_sax.h",
-        "xfa/fgas/xml/fgas_sax_imp.cpp",
-        "xfa/fgas/xml/fgas_sax_imp.h",
         "xfa/fwl/basewidget/fwl_barcodeimp.cpp",
         "xfa/fwl/basewidget/fwl_barcodeimp.h",
         "xfa/fwl/basewidget/fwl_caretimp.cpp",
         "xfa/fwl/basewidget/fwl_caretimp.h",
         "xfa/fwl/basewidget/fwl_checkboximp.cpp",
         "xfa/fwl/basewidget/fwl_checkboximp.h",
         "xfa/fwl/basewidget/fwl_comboboximp.cpp",
         "xfa/fwl/basewidget/fwl_comboboximp.h",
         "xfa/fwl/basewidget/fwl_datetimepickerimp.cpp",
         "xfa/fwl/basewidget/fwl_datetimepickerimp.h",
@@ skipping 624 matching lines @@
           "sources": [],
         }],
         ["OS == 'mac'", {
           "configurations": {},
           "sources": [],
         }],
       ]
     }
   ]
 }