[glom] Add -Wformat=2 to --enable-warnings=fatal.

[Murray Cumming <murrayc src gnome org>]

commit ff96025492cc5e5125f887b0a11ce868b256802e
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Feb 11 11:47:19 2016 +0100

    Add -Wformat=2 to --enable-warnings=fatal.
    
    It seems useful.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c7fd225..b37c30e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -223,7 +223,7 @@ MM_ARG_ENABLE_WARNINGS([GLOM_WFLAGS],
 AC_LANG([C++])
 MM_ARG_ENABLE_WARNINGS([GLOM_WXXFLAGS],
                        [-Wall],
-                       [-pedantic -Wall -Wextra -Wsuggest-override -Wshadow -Wformat-security -Wno-long-long 
-Wno-missing-field-initializers -DGSEAL_ENABLE],
+                       [-pedantic -Wall -Wextra -Wsuggest-override -Wshadow -Wformat-security -Wformat=2 
-Wno-long-long -Wno-missing-field-initializers -DGSEAL_ENABLE],
                        [G GDK GDK_PIXBUF GTK GDA GLIBMM GDKMM CAIROMM PANGOMM GTKMM SIGCXX LIBGDAMM])
 
 AC_CHECK_FUNCS([strptime])