Eliminate ASTContext's DelayInitialization flag

Having various possible states of initialization following construction doesn't
add value here.

Also remove the unused size_reserve parameter.

llvm-svn: 207897
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index e9672c4..76301f2 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -300,9 +300,9 @@
 void CompilerInstance::createASTContext() {
   Preprocessor &PP = getPreprocessor();
   Context = new ASTContext(getLangOpts(), PP.getSourceManager(),
-                           &getTarget(), PP.getIdentifierTable(),
-                           PP.getSelectorTable(), PP.getBuiltinInfo(),
-                           /*size_reserve=*/ 0);
+                           PP.getIdentifierTable(), PP.getSelectorTable(),
+                           PP.getBuiltinInfo());
+  Context->InitBuiltinTypes(getTarget());
 }
 
 // ExternalASTSource