[libclang] Properly expose linkage spec cursors

[cameron314]

Summary

All the groundwork for CXCursor_LinkageSpec already existed, but because of a missing case in a switch, cursors of that type were never actually created for linkage specifications in the AST. This patch fixes that.

I remember seeing another patch that fixed this a long time ago (that I found after fixing it myself), but it was never committed (it was just forgotten, if I recall correctly). Edit: Found it: http://lists.llvm.org/pipermail/cfe-dev/2014-July/038198.html

lib/Sema/SemaCodeComplete.cpp

case Decl::ClassTemplatePartialSpecialization:
       return CXCursor_ClassTemplatePartialSpecialization;
     case Decl::UsingDirective:     return CXCursor_UsingDirective;
     case Decl::TranslationUnit:    return CXCursor_TranslationUnit;
       
     case Decl::Using:
     case Decl::UnresolvedUsingValue:
     case Decl::UnresolvedUsingTypename: 
       return CXCursor_UsingDeclaration;
-      
+    case Decl::LinkageSpec:
+      return CXCursor_LinkageSpec;
+
     case Decl::ObjCPropertyImpl:
       switch (cast<ObjCPropertyImplDecl>(D)->getPropertyImplementation()) {
       case ObjCPropertyImplDecl::Dynamic:
         return CXCursor_ObjCDynamicDecl;
           
       case ObjCPropertyImplDecl::Synthesize:
         return CXCursor_ObjCSynthesizeDecl;
       }