[ClangImporter] Use the correct name for replacement decls.

When a C declaration is marked unavailable with a replacement, we look
for the replacement to see how it would be imported into Swift. Make
sure we do that with respect to the active language version.

Author: jrose-apple

lib/ClangImporter/ImportDecl.cpp

@@ -6516,7 +6516,7 @@ getSwiftNameFromClangName(StringRef replacement) {
   if (!clangDecl)
     return "";
 
-  auto importedName = importFullName(clangDecl, ImportNameVersion::Swift3);
+  auto importedName = importFullName(clangDecl, CurrentVersion);
   if (!importedName)
     return "";
 

test/APINotes/Inputs/custom-frameworks/APINotesFrameworkTest.framework/Headers/APINotesFrameworkTest.h

@@ -2,6 +2,8 @@ void jumpToLocation(double x, double y, double z);
 
 void acceptDoublePointer(double* _Nonnull ptr) __attribute__((swift_name("accept(_:)")));
 
+void oldAcceptDoublePointer(double* _Nonnull ptr) __attribute__((availability(swift, unavailable, replacement="acceptDoublePointer")));
+
 #ifdef __OBJC__
 
 __attribute__((objc_root_class))

test/APINotes/versioned.swift

@@ -39,4 +39,10 @@ func testRenamedTopLevel() {
   // CHECK-DIAGS-4: 'accept(_:)'
   // CHECK-DIAGS-3: 'acceptPointer(_:)'
   // CHECK-DIAGS: note: 'acceptDoublePointer' was obsoleted in Swift 3
+
+  oldAcceptDoublePointer(&value)
+  // CHECK-DIAGS: versioned.swift:[[@LINE-1]]:3: error: 'oldAcceptDoublePointer' has been renamed to
+  // CHECK-DIAGS-4: 'accept(_:)'
+  // CHECK-DIAGS-3: 'acceptPointer(_:)'
+  // CHECK-DIAGS: note: 'oldAcceptDoublePointer' has been explicitly marked unavailable here
 }