Replace use of malloc in string ports with a heap-allocated bytevector. Without this, if SEXP_USE_FINALIZERS=0, constructing output string ports without closing them would leak memory.  SEXP_USE_FINALIZERS=0 still requires caution when working with file-backed ports.
Replace use of malloc in string ports with a heap-allocated bytevector.
Without this, if SEXP_USE_FINALIZERS=0, constructing output string ports
without closing them would leak memory.  SEXP_USE_FINALIZERS=0 still
requires caution when working with file-backed ports.

norton/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme