[niepce] configure: update .m4. Add -Wformat as a warning

[Hubert Figuière <hub src gnome org>]

commit e44b432cd53bbaad82a547991f7ad4cd320f8014
Author: Hubert Figuière <hub figuiere net>
Date:   Wed May 10 22:02:52 2017 -0400

    configure: update .m4. Add -Wformat as a warning

 .gitignore                     |   12 +++++++++---
 configure.ac                   |    1 +
 m4/ax_append_compile_flags.m4  |   10 +++++-----
 m4/ax_cxx_compile_stdcxx_11.m4 |    8 ++++----
 4 files changed, 19 insertions(+), 12 deletions(-)
---
diff --git a/.gitignore b/.gitignore
index a525378..c69e085 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,9 +2,12 @@
 .deps
 Makefile
 Makefile.in
-config.guess
+ABOUT-NLS
 autogen.err
+compile
+config.guess
 config.log
+config.rpath
 config.sub
 config.status
 config.h
@@ -15,6 +18,9 @@ missing
 libtool
 depcomp
 install-sh
+intltool-extract.in
+intltool-merge.in
+intltool-update.in
 ltmain.sh
 test-driver
 test*.log
@@ -64,6 +70,7 @@ camerawire/po/POTFILES
 camerawire/po/Makefile.in
 doc/Doxyfile
 doc/doxygen/html
+po/*.pot
 po/*.gmo
 po/POTFILES
 po/Makefile.in.in
@@ -74,5 +81,4 @@ po/en@boldquot.header
 po/en@quot.header
 po/insert-header.sin
 po/quot.sed
-po/remove-potcdate.sed
-po/remove-potcdate.sin
+po/remove-potcdate.s*
diff --git a/configure.ac b/configure.ac
index 6ef8e14..39cce65 100644
--- a/configure.ac
+++ b/configure.ac
@@ -121,6 +121,7 @@ AX_APPEND_COMPILE_FLAGS([ \
    -Wcast-align \
    -Wextra \
    -Wheader-guard \
+   -Wformat \
    -Wformat-nonliteral \
    -Wformat-security \
    -Wlogical-not-parentheses \
diff --git a/m4/ax_append_compile_flags.m4 b/m4/ax_append_compile_flags.m4
index 2bb27ef..5b6f1af 100644
--- a/m4/ax_append_compile_flags.m4
+++ b/m4/ax_append_compile_flags.m4
@@ -1,6 +1,6 @@
-# ===========================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_append_compile_flags.html
-# ===========================================================================
+# ============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_append_compile_flags.html
+# ============================================================================
 #
 # SYNOPSIS
 #
@@ -41,7 +41,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -56,7 +56,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 5
+#serial 6
 
 AC_DEFUN([AX_APPEND_COMPILE_FLAGS],
 [AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
diff --git a/m4/ax_cxx_compile_stdcxx_11.m4 b/m4/ax_cxx_compile_stdcxx_11.m4
index 0aadeaf..1733fd8 100644
--- a/m4/ax_cxx_compile_stdcxx_11.m4
+++ b/m4/ax_cxx_compile_stdcxx_11.m4
@@ -1,6 +1,6 @@
-# ============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
-# ============================================================================
+# =============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
+# =============================================================================
 #
 # SYNOPSIS
 #
@@ -33,7 +33,7 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 17
+#serial 18
 
 AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
 AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [AX_CXX_COMPILE_STDCXX([11], [$1], [$2])])