Update RecursiveASTVisitor so that it visits attributes.  This is currently
important for thread safety attributes, which contain expressions that were
not being visited, and were thus invisible to various tools.  There are now
Visit*Attr methods that can be overridden for every attribute.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198224 91177308-0d34-0410-b5e6-96231b3b80d8
Remove linkage macro from the CXLanguageKind enum

Enums don't have linkage, so clang warns when this expands to dllimport.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198227 91177308-0d34-0410-b5e6-96231b3b80d8