Remove IFDE_TxtEdt interfaces where possible.

xfa.gyp

 {
   "variables": {
     "pdf_enable_v8%": 1,
   },
   "target_defaults": {
     "defines": [
       "PDF_ENABLE_XFA",
     ],
     'msvs_disabled_warnings': [
       4005, 4018, 4146, 4333, 4345, 4267,
@@ skipping 69 matching lines @@
         "xfa/fee/fde_txtedtengine.cpp",
         "xfa/fee/fde_txtedtengine.h",
         "xfa/fee/fde_txtedtpage.cpp",
         "xfa/fee/fde_txtedtpage.h",
         "xfa/fee/fde_txtedtparag.cpp",
         "xfa/fee/fde_txtedtparag.h",
         "xfa/fee/fx_wordbreak/fx_wordbreak.h",
         "xfa/fee/fx_wordbreak/fx_wordbreakdata.cpp",
         "xfa/fee/fx_wordbreak/fx_wordbreak_impl.cpp",
         "xfa/fee/fx_wordbreak/fx_wordbreak_impl.h",
-        "xfa/fee/ifde_txtedtbuf.h",
         "xfa/fee/ifde_txtedtengine.h",
         "xfa/fee/ifde_txtedtpage.h",
         "xfa/fgas/crt/fgas_algorithm.cpp",
         "xfa/fgas/crt/fgas_algorithm.h",
         "xfa/fgas/crt/fgas_codepage.cpp",
         "xfa/fgas/crt/fgas_codepage.h",
         "xfa/fgas/crt/fgas_encode.cpp",
         "xfa/fgas/crt/fgas_language.h",
         "xfa/fgas/crt/fgas_memory.cpp",
         "xfa/fgas/crt/fgas_memory.h",
@@ skipping 655 matching lines @@
           "sources": [],
         }],
         ["OS == 'mac'", {
           "configurations": {},
           "sources": [],
         }],
       ]
     }
   ]
 }