libsigc++: bump to 2.5.4

Signed-off-by: Steven Barth <steven@midlink.org>

libs/libsigc++/Makefile

@@ -8,12 +8,12 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libsigc++
-PKG_VERSION:=2.5.2
+PKG_VERSION:=2.5.4
 PKG_RELEASE:=1
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=@GNOME/libsigc++/2.5
-PKG_MD5SUM:=dfa12d53e4603504701866c256df84eb
+PKG_MD5SUM:=0b74492da5f640ab69888a984c6520d7
 PKG_MAINTAINER:=Steven Barth <cyrus@openwrt.org>
 PKG_LICENSE:=LGPL-2.1