[gthumb] show deprecated declarations warnings only when using --enable-debug

[Paolo Bacchilega <paobac src gnome org>]

commit ba6652238ab3e1d956412c1715df67acafd024ec
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Wed Aug 17 16:49:28 2016 +0200

    show deprecated declarations warnings only when using --enable-debug

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d40013b..c19db73 100644
--- a/configure.ac
+++ b/configure.ac
@@ -99,6 +99,8 @@ AC_ARG_ENABLE(debug,
 if test x$ENABLE_DEBUG = xyes; then
        AC_DEFINE(DEBUG, 1, [enable compilation of debugging messages])
        CFLAGS="$CFLAGS -g -O0 -DDEBUG"
+else
+       CFLAGS="$CFLAGS -Wno-deprecated-declarations"
 fi
 
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