add the exec permission and use tar.gz format for linux release

[id3nom]

Currently the linux binary release file are zip and the c3lsp binary don't have the execute permission,
zip is not always available on linux platform, which force the installation of another program the deflate the archive,
Also the execute permission is required to be able to execute a binary.

It would be better to add the read+execute permission 'chmod 0555 c3lsp' on the c3lsp binary and create a 'tar.gz' archive with a command like 'tar -czf c3lsp-linux-amd64.tar.gz ./release-dir-name', this would greatly improve the linux deployment.

[pherrymason]

Added the suggested changes to the pack-release goal of the make file.