If BIO_free() is called on a BIO chain it will only free one BIO resulting
in a memory leak.
-Calling BIO_free_all() a single BIO has the same effect as calling BIO_free()
-on it other than the discarded return value.
+Calling BIO_free_all() on a single BIO has the same effect as calling
+BIO_free() on it other than the discarded return value.
Normally the B<type> argument is supplied by a function which returns a
pointer to a BIO_METHOD. There is a naming convention for such functions: