[analyzer][NFC] Refactor functions in PlistDiagnostics to take Preproc as parameter
[analyzer][NFC] Refactor functions in PlistDiagnostics to take Preproc as parameter

This is patch is a preparation for the proposed inclusion of macro expansions in the plist output.

Differential Revision: https://reviews.llvm.org/D52735

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@343511 91177308-0d34-0410-b5e6-96231b3b80d8

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