rewrite BoolBinopNode for the non-boolean result case to avoid potentially harmful coercions along the way

move type coercion in BoolBinopNode chains from analyse_types() completely to coerce_to() as we may not know the final type that might support all operand types (usually boolean, but potentially user provided types)

--HG--
extra : transplant_source : %94%F6%D1%0B%19%00%C5%87%83%0Dl%A4U%8Db%19r%E7%5C%DD

--HG--
extra : transplant_source : %97s8%E8ep%83%1E%3BGo%1C%C8%11%A67%81Y%0B%DD

complete struct stat in POSIX API

generally postpone the cleanup for char* temps to improve safety and move the 'char* from temp' compile error to assignments to allow non-trivial char* expressions

--HG--
rename : tests/run/charptr_cfunc_args.pyx => tests/run/charptr_from_temp.pyx

keep Python string object references alive across temp cleanup until disposal (e.g. during function calls that take them as arguments)