Update slang for LLVM rebase to r230699.

Change-Id: I6fa2c59b1445735e2eb95deb4ac503cb9ed369ee
diff --git a/slang_rs_context.cpp b/slang_rs_context.cpp
index 608d6cb..81b3b49 100644
--- a/slang_rs_context.cpp
+++ b/slang_rs_context.cpp
@@ -132,10 +132,10 @@
     //             found
     return false;
 
-  clang::DeclContext::lookup_const_result R = TUDecl->lookup(II);
+  clang::DeclContext::lookup_result R = TUDecl->lookup(II);
   RSExportType *ET = nullptr;
 
-  for (clang::DeclContext::lookup_const_iterator I = R.begin(), E = R.end();
+  for (clang::DeclContext::lookup_iterator I = R.begin(), E = R.end();
        I != E;
        I++) {
     clang::NamedDecl *const ND = *I;