[gnumeric] Compilation: fix clang compilation.

[Morten Welinder <mortenw src gnome org>]

commit b11a1aeaa11951f20f48838c5725738704cc4e1f
Author: Morten Welinder <terra gnome org>
Date:   Mon May 11 22:12:30 2015 -0400

    Compilation: fix clang compilation.

 ChangeLog     |    3 +++
 configure.ac  |    2 +-
 src/wbc-gtk.c |    3 ++-
 3 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index dc6e86f..948d500 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2015-05-11  Morten Welinder  <terra gnome org>
 
+       * src/wbc-gtk.c (wbcg_validation_msg): Fix clang warning about
+       something bad that will happen whenever FALSE equals TRUE.
+
        * src/go-data-cache.c (go_data_cache_set_val): Use memcpy for
        inline values.
 
diff --git a/configure.ac b/configure.ac
index c7220c2..129924e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -285,7 +285,7 @@ if test "$GCC" = yes -a "x$set_more_warnings" != xno; then
                         -Werror=format-security -Wbitwise -Wcast-to-as \
                         -Wdefault-bitfield-sign -Wdo-while -Wparen-string \
                         -Wptr-subtraction-blows -Wreturn-void -Wtypesign \
-                        -Wstrict-prototypes"
+                        -Wstrict-prototypes -Wno-error=format-nonliteral "
        for option in $warning_options ; do
                SAVE_CFLAGS="$CFLAGS"
                CFLAGS="$CFLAGS $uwoption $option"
diff --git a/src/wbc-gtk.c b/src/wbc-gtk.c
index 1ad2f71..19158af 100644
--- a/src/wbc-gtk.c
+++ b/src/wbc-gtk.c
@@ -2893,7 +2893,8 @@ wbcg_validation_msg (WorkbookControl *wbc, ValidationStyle v,
                type = GTK_MESSAGE_ERROR;
                break;
 
-       default : g_return_val_if_fail (FALSE, 1);
+       default:
+               g_assert_not_reached ();
        }
 
        dialog = gtk_message_dialog_new (wbcg_toplevel (wbcg),