Sort environment variables in binary output
Documented the -bf-data-structs command-line option
Don't attempt to demangle names that don't look mangled

The __cxa_demangle() function demangles "f" to "float" and "n" to
"__int64".  Byfl's demangle_func_name() wrapper now skips passing
__cxa_demangle() names that don't begin with "_Z", which is how g++
begins all mangled names.