irix6.5 bootstrap failure - vscanf and vsscanf not declared

["Billinghurst, David (CRTS)" <David dot Billinghurst at riotinto dot com>]

irix6.5 bootstrap on branch fails with 

/exd4/billingd/obj/gcc/gcc/xgcc -B/exd4/billingd/obj/gcc/gcc/ -nostdinc++
-L/exd4/billingd/obj/gcc/mips-sgi-irix6.5/libstdc++-v3/src
-L/exd4/billingd/obj/gcc/mips-sgi-irix6.5/libstdc++-v3/src/.libs
-B/exd4/billingd/tmp/gcc/mips-sgi-irix6.5/bin/
-B/exd4/billingd/tmp/gcc/mips-sgi-irix6.5/lib/ -isystem
/exd4/billingd/tmp/gcc/mips-sgi-irix6.5/include -nostdinc++
-I/exd4/billingd/src/gcc/libstdc++-v3/include
-I/exd4/billingd/src/gcc/libstdc++-v3/include/std
-I/exd4/billingd/src/gcc/libstdc++-v3/include/c_std -I../include
-I/exd4/billingd/src/gcc/libstdc++-v3/libsupc++ -I../libio
-I/exd4/billingd/src/gcc/libstdc++-v3/libio
-I/exd4/billingd/src/gcc/libstdc++-v3/libmath -g -O2 -fno-implicit-templates
-Wall -Wno-format -W -Wwrite-strings -Winline
-fdiagnostics-show-location=once -ffunction-sections -fdata-sections -g -c
/exd4/billingd/src/gcc/libstdc++-v3/src/stdexcept.cc   -DPIC -o
.libs/stdexcept.o
In file included from
/exd4/billingd/src/gcc/libstdc++-v3/include/std/cstdio:31,
                 from ../include/bits/c++io.h:35,
                 from
/exd4/billingd/src/gcc/libstdc++-v3/include/bits/fpos.h:39,
                 from
/exd4/billingd/src/gcc/libstdc++-v3/include/bits/char_traits.h:40,
                 from
/exd4/billingd/src/gcc/libstdc++-v3/include/bits/std_string.h:41,
                 from
/exd4/billingd/src/gcc/libstdc++-v3/src/stdexcept.cc:34:/exd4/billingd/src/g
cc/libstdc++-v3/include/c_std/bits/std_cstdio.h:108: `vfscanf'   not
declared
/exd4/billingd/src/gcc/libstdc++-v3/include/c_std/bits/std_cstdio.h:110:
`vscanf'   not declared
/exd4/billingd/src/gcc/libstdc++-v3/include/c_std/bits/std_cstdio.h:112:
`vsscanf'   not declared      

AFAICT irix6.5 does not supply vscanf and vsscanf.  No mention in man pages
or in /usr/include.