Added SHA256 checksum to stackless-2.7.9

plugins/python-build/share/python-build/stackless-2.7.9

@@ -1,4 +1,4 @@
 #require_gcc
 install_package "openssl-1.0.2g" "https://www.openssl.org/source/openssl-1.0.2g.tar.gz#b784b1b3907ce39abf4098702dade6365522a253ad1552e267a9a0e89594aa33" mac_openssl --if has_broken_mac_openssl
 install_package "readline-6.3" "https://ftpmirror.gnu.org/readline/readline-6.3.tar.gz#56ba6071b9462f980c5a72ab0023893b65ba6debb4eeb475d7a563dc65cafd43" standard --if has_broken_mac_readline
-install_package "stackless-dev-stackless-43302de87df4" "https://bitbucket.org/stackless-dev/stackless/get/v2.7.9-slp.tar.bz2" ldflags_dirs standard verify_py27 ensurepip
+install_package "stackless-dev-stackless-43302de87df4" "https://bitbucket.org/stackless-dev/stackless/get/v2.7.9-slp.tar.bz2#83857fb269a59cca51c68aef84295892f86ce775700dbe9a3f7fe8322f7dd6ff" ldflags_dirs standard verify_py27 ensurepip