Gmp now working, but number.c:147 isinf declared implicitly.

[Hugh Sasse]

I am now getting :

 gcc -DHAVE_CONFIG_H -I. -I. -I.. -I.. -I.. -D_REENTRANT -pthreads -g -O2 -Wall 
-Wmissing-prototypes -Werror -MT libguile_la-numbers.lo -MD -MP -MF 
.deps/libguile_la-numbers.Tpo -c numbers.c  -fPIC -DPIC -o 
.libs/libguile_la-numbers.o
cc1: warnings being treated as errors
numbers.c: In function 'xisinf':
numbers.c:147: warning: implicit declaration of function 'isinf'
gmake[3]: *** [libguile_la-numbers.lo] Error 1
gmake[3]: Leaving directory `/export/home/Scratch/hgs/guile-1.8.1/libguile'
gmake[2]: *** [all] Error 2

$ ggrep -C 8 isinf config.log
| int
| main ()
| {
| return trunc ();
|   ;
|   return 0;
| }
configure:43674: result: no
configure:43694: checking for isinf
configure:43706: gcc -o conftest -g -O2   conftest.c -lgmp -lsocket -lnsl -lm 
-lltdl  >&5
configure:43712: $? = 0
configure:43719: test -z "$ac_c_werror_flag" || test ! -s conftest.err
configure:43722: $? = 0
configure:43729: test -s conftest
configure:43732: $? = 0
configure:43734: result: yes
configure:43751: checking for isnan
$
So configure knwo what it is, but I can't see how to get at this info 
to modify number.c.  Maybe I need to do something different?

        Thank you,
        Hugh