Remove deprecated HDFS support

cmake/modules/Findhdfs.cmake

cmake/modules/RootBuildOptions.cmake

cmake/modules/RootConfiguration.cmake

cmake/modules/SearchInstalledSoftware.cmake

config/Makefile.in

documentation/doxygen/Doxyfile

etc/plugins/TFile/P110_THDFSFile.C

etc/plugins/TSystem/P060_THDFSSystem.C

io/CMakeLists.txt

io/hdfs/CMakeLists.txt

io/hdfs/doc/index.html

io/hdfs/inc/LinkDef.h

io/hdfs/inc/THDFSFile.h

io/hdfs/src/THDFSFile.cxx

io/io/src/TMemFile.cxx