Add support for __declspec(code_seg("segname"))
This patch is built on the existing support for #pragma code_seg. The code_seg declspec is allowed on functions and classes. The attribute enables the placement of code into separate named segments, including compiler-generated members and template instantiations.
For more information, please see the following:
A new CodeSeg attribute is used instead of adding a new spelling to the existing Section attribute since they don’t apply to the same Subjects. Section attributes are also added for the code_seg declspec since they are used for #pragma code_seg. No CodeSeg attributes are added to the AST.
The patch is written to match with the Microsoft compiler’s behavior even where that behavior is a little complicated (see https://reviews.llvm.org/D22931, the Microsoft feedback page is no longer available since MS has removed the page). That code is in getImplicitSectionAttrFromClass routine.
Diagnostics messages are added to match with the Microsoft compiler for code-seg attribute mismatches on base and derived classes and virtual overrides.