nails don't work with GMP 5

[Paul Zimmermann]

       Hi,

it seems nails don't work any more with GMP 5:

[zimmerma at coing gmp-5.0.0]$ ./config.guess 
core2-unknown-linux-gnu

[zimmerma at coing gmp-5.0.0]$ ./configure --enable-nails=2
...
 gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I. -I.. -D__GMP_WITHIN_GMP -I.. -DOPERATION_hgcd2 -O2 -pedantic -m64 -mtune=core2 -march=core2 -c hgcd2.c  -fPIC -DPIC -o .libs/hgcd2.o
hgcd2.c:197:2: error: #error Not implemented
hgcd2.c: In function '__gmpn_hgcd2':
hgcd2.c:277: warning: implicit declaration of function 'div2'
hgcd2.c:357: warning: implicit declaration of function 'div1'
make[2]: *** [hgcd2.lo] Error 1

Paul Zimmermann