package/gsl: bump version to 2.5

Added license hash.

Release notes:
https://lists.gnu.org/archive/html/info-gnu/2018-06/msg00007.html

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/gsl/gsl.hash

@@ -1,2 +1,3 @@
 # Locally calculated after checking pgp signature
-sha256 562500b789cd599b3a4f88547a7a3280538ab2ff4939504c8b4ac4ca25feadfb  gsl-2.3.tar.gz
+sha256 0460ad7c2542caaddc6729762952d345374784100223995eb14d614861f2258d  gsl-2.5.tar.gz
+sha256 8ceb4b9ee5adedde47b31e975c1d90c73ad27b6b165a1dcd80c7c545eb65b903  COPYING

package/gsl/gsl.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-GSL_VERSION = 2.3
+GSL_VERSION = 2.5
 GSL_SITE = $(BR2_GNU_MIRROR)/gsl
 GSL_INSTALL_STAGING = YES
 GSL_LICENSE = GPL-3.0