[goffice] Math: use rint in go_rint.

[Morten Welinder <mortenw src gnome org>]

commit 6bb793ee336673ff5c0fd1433a7e99d7c46c0089
Author: Morten Welinder <terra gnome org>
Date:   Wed Apr 2 20:22:45 2014 -0400

    Math: use rint in go_rint.
    
    This avoids stick issues with 2^51, for example.

 ChangeLog              |    1 +
 configure.ac           |    2 +-
 goffice/math/go-math.c |    4 ++++
 3 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 7d973c9..87da0e9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@
        * goffice/math/go-math.c (go_fake_round): Fix problem for 2^51 and
        like integers.
        (go_fake_roundl): Ditto, although for different set of numbers.
+       (go_rint): Just use rint.
 
        * tests/test-format.c: New test program.
 
diff --git a/configure.ac b/configure.ac
index 708d58f..c9b56c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -565,7 +565,7 @@ if test $ac_cv_func_log = no; then
          LIBS="$LIBS -lm"])
 fi
 
-AC_CHECK_FUNCS(nextafter nextafterl)
+AC_CHECK_FUNCS(nextafter nextafterl rint)
 
 SAVE_CFLAGS=$CFLAGS
 SAVE_LIBS=$LIBS
diff --git a/goffice/math/go-math.c b/goffice/math/go-math.c
index 926bc52..5fc01a4 100644
--- a/goffice/math/go-math.c
+++ b/goffice/math/go-math.c
@@ -300,8 +300,12 @@ go_fake_trunc (double x)
 double
 go_rint (double x)
 {
+#ifdef HAVE_RINT
+       return rint (x);
+#else
        double y = floor (fabs (x) + 0.5);
        return (x < 0) ? -y : y;
+#endif
 }
 
 int