[gnome-calculator] build: Require mpfr.h

[Arth Patel <arthpatel src gnome org>]

commit 58e34ab92c1d83e11464df624e8239c6b55fce43
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Dec 22 21:42:28 2014 +0000

    build: Require mpfr.h
    
    The MPFR library is a requirement, but since it does not ship with a
    pkg-config file, we need to do a check on the header.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=741880

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c0b08f7..74ce6d2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -22,6 +22,8 @@ GLIB_REQUIRED=2.40.0
 GTK_REQUIRED=3.11.6
 GTKSOURCEVIEW_REQUIRED=3.15.1
 
+AC_CHECK_HEADER([mpfr.h], [], [AC_MSG_ERROR([The mpfr header is missing. Please, install mpfr])])
+
 PKG_CHECK_MODULES(GNOME_CALCULATOR, [
     gtk+-3.0 >= $GTK_REQUIRED
     glib-2.0 >= $GLIB_REQUIRED