treewide: Change .*GPL.*+ licenses to SPDX compatible identifier

The CONTRIBUTING.md requests an (or multiple) SPDX identifier for GPL
licenses. But a lot of packages did use a different, non-SPDX style with a
"+" at the end instead of "-or-later".

Signed-off-by: Sven Eckelmann <sven@narfation.org>

libs/libplist/Makefile

@@ -9,10 +9,10 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libplist
 PKG_VERSION:=2.0.0
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_MAINTAINER:=Lukasz Baj <l.baj@radytek.com>
-PKG_LICENSE:=LGPL-2.1+
+PKG_LICENSE:=LGPL-2.1-or-later
 PKG_LICENSE_FILES:=COPYING.LESSER
 
 PKG_SOURCE_PROTO:=git