openpgm: bump to version release-5-2-122

At the same time perform a GitHub migration, since Google Code will
disappear soon.

- Bump to version release-5-2-122
- Switch to GitHub
- Remove trailing slash from OPENPGM_SUBDIR
- Remove unnecessary python dependencies
- Add a hook to create the missing m4 directory, needed to autoreconf
- Add a hash file
- Rewrap the help text to 72 characters length
- Change the project URL

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>