better configure check for long double support

configure

@@ -706,9 +706,8 @@ esac
 #
 printf "checking whether compiler's long double definition matches float.h... "
 echo '#include <float.h>' > "$tmpc"
-echo '#if LDBL_MANT_DIG == 53' >> "$tmpc"
-echo 'typedef char ldcheck[9-(int)sizeof(long double)];' >> "$tmpc"
-echo '#endif' >> "$tmpc"
+echo '#define C(m,s) (m==LDBL_MANT_DIG && s==sizeof(long double))' >> "$tmpc"
+echo 'typedef char ldcheck[(C(53,8)||C(64,12)||C(64,16)||C(113,16))*2-1];' >> "$tmpc"
 if $CC $CFLAGS_C99FSE \
   -I$srcdir/arch/$ARCH -I$srcdir/arch/generic -I$srcdir/include \
   $CPPFLAGS $CFLAGS -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then