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>

lang/python/python-gnupg/Makefile

@@ -6,13 +6,13 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=python-gnupg
 PKG_VERSION:=0.4.4
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://files.pythonhosted.org/packages/source/p/python-gnupg
 PKG_HASH:=45daf020b370bda13a1429c859fcdff0b766c0576844211446f9266cae97fb0e
 
-PKG_LICENSE:=GPL-3.0+
+PKG_LICENSE:=GPL-3.0-or-later
 PKG_LICENSE_FILES:=LICENSE
 PKG_MAINTAINER:=Daniel Golle <daniel@makrotopia.org>