Remove deprecated RFIO support

cmake/modules/RootBuildOptions.cmake

cmake/modules/RootConfiguration.cmake

cmake/modules/SearchInstalledSoftware.cmake

config/Makefile.in

config/mimes.unix.in

config/mimes.win32.in

config/rootrc.in

core/base/inc/MessageTypes.h

core/base/inc/TPluginManager.h

core/base/src/TPluginManager.cxx

core/base/src/TSystem.cxx

core/base/src/TUrl.cxx

documentation/doxygen/Doxyfile

etc/plugins/TFile/P020_TRFIOFile.C

etc/plugins/TSystem/P010_TRFIOSystem.C

io/CMakeLists.txt

io/gfal/src/TGFALFile.cxx

io/io/src/TFile.cxx

io/io/src/TFileMerger.cxx

io/rfio/CMakeLists.txt