Add a fallback definition for mpn_sqr.

ChangeLog

@@ -3,6 +3,7 @@
 	From Martin Storsjö. Fallback functions for older GMP releases.
 	* gmp-glue.c (mpn_copyd, mpn_copyi, mpn_zero): New functions.
 	* gmp-glue.h: Declare them.
+	(mpn_sqr): Fallback macro.
 
 	* gmp-glue.h (cnd_add_n, cnd_sub_n): Moved here, define in terms
 	of mpn_cnd_add_n and mpn_sub_n if available, otherwise in terms of

gmp-glue.h

@@ -54,6 +54,10 @@
 #define mpn_zero  _nettle_mpn_zero
 #endif
 
+#ifndef mpn_sqr
+#define mpn_sqr(rp, ap, n) mpn_mul_n((rp), (ap), (ap), (n))
+#endif
+
 #define mpz_limbs_cmp _nettle_mpz_limbs_cmp
 #define mpz_limbs_read_n _nettle_mpz_limbs_read_n
 #define mpz_limbs_copy _nettle_mpz_limbs_copy