* newlib.hin (_FVWRITE_IN_STREAMIO): Undefine.
* configure.in (--disable-newlib-fvwrite-in-streamio): New option.
* configure: Regenerated.
* libc/stdio/fputs.c (_fputs_r): Use _FVWRITE_IN_STREAMIO to
control __sfvwrite_r. Add alternative implementation.
* libc/stdio/fputws.c (_fputws_r): Ditto.
* libc/stdio/fwrite.c (_fwrite_r): Ditto.
* libc/stdio/puts.c (_puts_r): Ditto.
* libc/stdio/vfprintf.c (__ssputs_r, __sfputs_r): New function.
(_VFPRINTF_R): Use _FVWRITE_IN_STREAMIO to control vector buffer.
(__SPRINT): Use _FVWRITE_IN_STREAMIO to control macro definition.
* libc/stdio/vfwprintf.c (_VFWPRINTF_R): Use _FVWRITE_IN_STREAMIO
to control vector buffer.
secure stream related critical section against thread cancellation.
(_newlib_flockfile_exit): Ditto.
(_newlib_sfp_lock_end): Ditto.
(_newlib_sfp_lock_start): Ditto for the list of streams.
(_newlib_sfp_lock_exit): Ditto.
(_newlib_sfp_lock_end): Ditto.
Use aforementioned macros in place of _flockfile/_funlockfile
and __sfp_lock_acquire/__sfp_lock_release throughout the code.
* libc/stdio/fclose.c: Explicitely disable and re-enable thread
cancellation. Explain why.
* libc/stdio/freopen.c: Ditto.
* libc/stdio64/freopen64.c: Ditto.