Update gmp

Author: certik

pkgs/gmp.yaml

@@ -4,8 +4,8 @@ dependencies:
   build: [m4]
 
 sources:
-- url: http://mirrors.kernel.org/gnu/gmp/gmp-5.1.3.tar.bz2
-  key: tar.bz2:ouqhsuqli2ifgelr2d2fglsa6cdaaik7
+- key: tar.bz2:p6hjvacltrwqofsm65kca67ihdwocimu
+  url: http://mirrors.kernel.org/gnu/gmp/gmp-6.0.0a.tar.bz2
 
 build_stages:
 - name: configure