re PR go/89598 (go frontend fails to build against mpfr 2.4.2)

	PR go/89598
    compiler: use GMP_RNDN rather than MPFR_RNDN
    
    This fixes the build with mpfr 2.4.2.
    
    Fixes https://gcc.gnu.org/PR89598
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/165418

From-SVN: r269399

gcc/go/gofrontend/MERGE

-decbbfb563ecf4609a3148dc789ae77ab1c62768
+689d5bda159300dc12f559de2d47b8c1c762fcb9
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -17287,8 +17287,8 @@ Numeric_constant::hash(unsigned int seed) const
       break;
     case NC_COMPLEX:
       mpfr_init(m);
-      mpc_abs(m, this->u_.complex_val, MPFR_RNDN);
-      val = mpfr_get_ui(m, MPFR_RNDN);
+      mpc_abs(m, this->u_.complex_val, GMP_RNDN);
+      val = mpfr_get_ui(m, GMP_RNDN);
       mpfr_clear(m);
       break;
     case NC_FLOAT: