hgrc.d: separate namespace for mercurial scripts 9diff and 9mail

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extra : rebase_source : 15f9cbfbe759f3aaeb1dba709c4a8be112dfa279
Backed out changeset 77d434760857

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extra : rebase_source : 30af6672fce0327bfeb1267fe4dcbfba7eb8a3de