Make sure we look through categories when searching for a classes property.

Fixes <rdar://problem/5984338> clang on xcode: property implementation must have its declaration in interface 'PBXOpenQuicklyModule'


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@51925 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/DeclObjC.cpp b/lib/AST/DeclObjC.cpp
index 701ad35..e493d27 100644
--- a/lib/AST/DeclObjC.cpp
+++ b/lib/AST/DeclObjC.cpp
@@ -150,6 +150,13 @@
     if (property->getIdentifier() == PropertyId)
       return property;
   }
+  // Look through categories.
+  for (ObjCCategoryDecl *Category = getCategoryList();
+       Category; Category = Category->getNextClassCategory()) {
+    ObjCPropertyDecl *property = Category->FindPropertyDeclaration(PropertyId);
+    if (property)
+      return property;
+  }
   if (getSuperClass())
     return getSuperClass()->FindPropertyDeclaration(PropertyId);
   return 0;