[rhythmbox] add -DGSEAL_ENABLE for development builds with new enough gtk+

[Jonathan Matthew <jmatthew src gnome org>]

commit ee05ea0933aca20256967ef7801947cab00033ee
Author: Jonathan Matthew <jonathan d14n org>
Date:   Mon Mar 29 23:19:22 2010 +1000

    add -DGSEAL_ENABLE for development builds with new enough gtk+
    
    When building from a VCS checkout or when --enable-more-warnings was
    passed to ./configure, and gtk+ is new enough (2.20.0), enable GSEAL.

 configure.ac |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 990e57e..f05ebf5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -577,6 +577,9 @@ if test "$GCC" = "yes" -a "$set_more_warnings" != "no"; then
 	CFLAGS="$SAVE_CFLAGS"
 	unset SAVE_CFLAGS
 	unset has_wnoerror
+
+	dnl enable GSEAL if gtk is new enough
+	PKG_CHECK_EXISTS(gtk+-2.0 >= 2.20.0, [CFLAGS="$CFLAGS -DGSEAL_ENABLE"], [])
 else
 	AC_MSG_RESULT(no)
 fi