[codeview] Describe int local variables using .cv_def_range

Summary:
Refactor common value, scope, and label tracking logic out of DwarfDebug
into a common base class called DebugHandlerBase.

Update an old LLVM IR test case to avoid an assertion in LexicalScopes.

Reviewers: dblaikie, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D16931

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260432 91177308-0d34-0410-b5e6-96231b3b80d8
19 files changed