package/gnuchess: security bump to version 6.2.7

package/gnuchess: security bump to version 6.2.7

Fix CVE-2019-15767: In GNU Chess 6.2.5, there is a stack-based buffer
overflow in the cmd_load function in frontend/cmd.cc via a crafted chess
position in an EPD file.

Update indentation in hash file (two spaces)

https://lists.gnu.org/archive/html/info-gnu-chess/2020-04/msg00000.html
https://lists.gnu.org/archive/html/info-gnu-chess/2020-05/msg00000.html

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>