[docs] AliasAnalysis: clarify that PartialAlias doesn't enforce objects to start at the same address
[docs] AliasAnalysis: clarify that PartialAlias doesn't enforce
objects to start at the same address

As discussed on the ML, there's consensus that this is what the implementations
do and it seems sensible.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@308090 91177308-0d34-0410-b5e6-96231b3b80d8

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