[niepce] configure: require GEGL 0.4 and add -Wclass-memaccess

[Hubert Figuière <hub src gnome org>]

commit 0cdc339dd5eabebe3475330cb176aaec8c3517aa
Author: Hubert Figuière <hub figuiere net>
Date:   Thu Sep 26 22:13:30 2019 -0400

    configure: require GEGL 0.4 and add -Wclass-memaccess

 configure.ac | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index 1ccc5e0..8a61872 100644
--- a/configure.ac
+++ b/configure.ac
@@ -69,7 +69,7 @@ PKG_CHECK_MODULES(OPENRAW, libopenraw-0.1 >= $LIBOPENRAW_VERSION)
 AC_SUBST(OPENRAW_CFLAGS)
 AC_SUBST(OPENRAW_LIBS)
 
-PKG_CHECK_MODULES(GEGL, gegl-0.3 >= $GEGL_VERSION)
+PKG_CHECK_MODULES(GEGL, gegl-0.4 >= $GEGL_VERSION)
 AC_SUBST(GEGL_CFLAGS)
 AC_SUBST(GEGL_LIBS)
 
@@ -94,6 +94,7 @@ AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option], [
 AX_APPEND_COMPILE_FLAGS([ \
    -Wchar-subscripts \
    -Wcast-align \
+   -Wclass-memaccess \
 dnl sigc++ 2.10.0 breaks with that warning.
    -Wno-cast-function-type \
    -Wextra \