Revert "Decouple dllexport/dllimport from linkage"

Revert this for now until I fix an issue in Clang with it.

This reverts commit r199204.

llvm-svn: 199207
diff --git a/llvm/include/llvm-c/Core.h b/llvm/include/llvm-c/Core.h
index a84a031..269869e 100644
--- a/llvm/include/llvm-c/Core.h
+++ b/llvm/include/llvm-c/Core.h
@@ -284,8 +284,8 @@
   LLVMInternalLinkage,    /**< Rename collisions when linking (static
                                functions) */
   LLVMPrivateLinkage,     /**< Like Internal, but omit from symbol table */
-  LLVMDLLImportLinkage,   /**< Obsolete */
-  LLVMDLLExportLinkage,   /**< Obsolete */
+  LLVMDLLImportLinkage,   /**< Function to be imported from DLL */
+  LLVMDLLExportLinkage,   /**< Function to be accessible from DLL */
   LLVMExternalWeakLinkage,/**< ExternalWeak linkage description */
   LLVMGhostLinkage,       /**< Obsolete */
   LLVMCommonLinkage,      /**< Tentative definitions */