minor: update readme for 26compat branch
CXX-65 Remove mongo/util/log.h from pch.h
CXX-65 Remove mongo/util/allocator.h from pch.h and elsewhere
CXX-65 Remove mongo/util/goodies.h from pch.h
CXX-65 Remove mongo/util/assert_util.h from pch.h
CXX-65 Remove mongo/util/debug_util.h from pch.h
CXX-65 Remove boost/version.hpp from pch.h
CXX-65 Remove boost/bind.hpp from pch.h
CXX-65 Remove boost/smart_ptr.hpp from pch.h
CXX-65 Remove boost/shared_ptr.hpp from pch.h
CXX-65 Filesystem v3 is the default in our boost minimum of 1.49
CXX-65 Remove iostream from pch.h
CXX-65 Remove C++ container headers from pch.h
CXX-65 Remove memory from pch.h
CXX-65 Remove cstring from pch.h
CXX-65 Remove C headers from pch.h
CXX-65 Remove mongo/platform/basic.h from pch.h
CXX-65 Remove exit nonsense from pch.h
CXX-65 Remove export_macros.h from pch.h
CXX-65 Remove boost usings from goodies.h and other headers