fails to compile with undefined symbol (FP_PLUS_INF)

when compiling psql 8.1.3 using gcc 3.4.5 on AIX 4.2.1 on powerpc32 I
get the following error:

gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Winline
-Wdeclaration-after-statement -Wendif-labels -fno-strict-aliasing
-I../../src/port -DFRONTEND -I../../src/include -I/usr/local/include 
-c isinf.c -o isinf.o
isinf.c: In function `isinf':
isinf.c:69: error: `FP_PLUS_INF' undeclared (first use in this function)
isinf.c:69: error: (Each undeclared identifier is reported only once
isinf.c:69: error: for each function it appears in.)
isinf.c:71: error: `FP_MINUS_INF' undeclared (first use in this function)
make[2]: *** [isinf.o] Error 1


configure options where:
./configure --with-includes=/usr/local/include
--with-libs=/usr/local/lib --without-readline

any ideas? patches? is this already known?

thanks,
  Riccardo