More #include cleaning

- Drop Expr.h,RecordLayout.h from ASTContext.h (for DeclBase.h and
   SourceLocation.h)
 - Move ASTContext constructor into implementation

llvm-svn: 54627

clang/lib/Sema/Sema.cpp

@@ -14,6 +14,7 @@
 
 #include "Sema.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Parse/Scope.h"