[linuxsh-dev] Tag 2.5.0 and 2.5.1

[NIIBE Y. <gn...@m1...>]

I'll add the tag linux-2_5_0 for the current repository.
Then, install the changes of mainline 2.5.0 to 2.5.1, and
remove the file AGAINST-2.5.0 and add AGAINST-2.5.1.
Also, rotate the ChangeLog files.
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