BUG: force TIXML_USE_STL to always true in otb_tinyxml.h
TIXML_USE_STL to false is completely useless because OTB depends on the STL. Because of !487 (merged), this causes a build error in OTB 7.0.0 when using a tinyxml not from the SuperBuild (because it was set to ON in
- Force TIXML_USE_STL to true in otb_tinyxml.h
- Remove support and compiler checking for setting TIXML_USE_STL from CMake.