[clang] [SystemZ][z/OS] Add visibility features for z/OS (eg. _Export, pragma export) (PR #111035)

[Sean Perry via cfe-commits]

================
@@ -401,6 +401,12 @@ struct PragmaMaxTokensTotalHandler : public PragmaHandler {
                     Token &FirstToken) override;
 };
 
+struct PragmaExportHandler : public PragmaHandler {
----------------
perry-ca wrote:

Ok.  Multiple requests now.  I'll move the keyword _Export into a new PR.  Do you prefer two new ones or keep this one going just for the pragma?

https://github.com/llvm/llvm-project/pull/111035