[analyzer][NFC] Add dividers to BugReporterVisitors.cpp
[analyzer][NFC] Add dividers to BugReporterVisitors.cpp

Some minor formatting to make the file more readable.
Added //===----------===// around the implementation of class methods
and divided anonymous namespaces as per
https://llvm.org/docs/CodingStandards.html#anonymous-namespaces

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@362887 91177308-0d34-0410-b5e6-96231b3b80d8

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