package/sdl2: bump version to 2.0.20

Copyright year updated in LICENSE.txt.

Signed-off-by: Michael Fischer <mf@go-sys.de>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/sdl2/sdl2.hash

@@ -1,4 +1,4 @@
-# Locally calculated after checking http://www.libsdl.org/release/SDL2-2.0.18.tar.gz.sig
-sha256  94d40cd73dbfa10bb6eadfbc28f355992bb2d6ef6761ad9d4074eff95ee5711c  SDL2-2.0.18.tar.gz
+# Locally calculated after checking http://www.libsdl.org/release/SDL2-2.0.20.tar.gz.sig
+sha256  c56aba1d7b5b0e7e999e4a7698c70b63a3394ff9704b5f6e1c57e0c16f04dd06  SDL2-2.0.20.tar.gz
 # Locally calculated
-sha256  52d41d0c82507721ca1fd92c20dc2bf9ca531b3a288ef845a8275c550f118804  LICENSE.txt
+sha256  fcb07e07ac6bc8b2fcf047b50431ef4ebe5b619d7ca7c82212018309a9067426  LICENSE.txt

package/sdl2/sdl2.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-SDL2_VERSION = 2.0.18
+SDL2_VERSION = 2.0.20
 SDL2_SOURCE = SDL2-$(SDL2_VERSION).tar.gz
 SDL2_SITE = http://www.libsdl.org/release
 SDL2_LICENSE = Zlib