talloc: add defines and functions for TALLOC_MAJOR/MINOR_VERSION

talloc: add defines and functions for TALLOC_MAJOR/MINOR_VERSION

We also use the major and minor versions in the TALLOC_MAGIC,
so that we can detect if two conflicting versions of talloc
are loaded in one process. In this case we use talloc_log() to
output a very useful debug message before we call
talloc_abort().

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