Do not print include_next/pragma once warnings when input is a header.

r276653 suppressed the pragma once warning when generating a PCH file.
This patch extends that to any main file for which clang is told (with
the -x option) that it's a header file. It will also suppress the
warning "#include_next in primary source file".

Differential Revision: http://reviews.llvm.org/D25989

llvm-svn: 285295
diff --git a/clang/lib/Basic/LangOptions.cpp b/clang/lib/Basic/LangOptions.cpp
index 59cee6c..ff10a77 100644
--- a/clang/lib/Basic/LangOptions.cpp
+++ b/clang/lib/Basic/LangOptions.cpp
@@ -15,7 +15,8 @@
 
 using namespace clang;
 
-LangOptions::LangOptions() {
+LangOptions::LangOptions()
+  : IsHeaderFile(false) {
 #define LANGOPT(Name, Bits, Default, Description) Name = Default;
 #define ENUM_LANGOPT(Name, Type, Bits, Default, Description) set##Name(Default);
 #include "clang/Basic/LangOptions.def"
@@ -34,6 +35,7 @@
   SanitizerBlacklistFiles.clear();
 
   CurrentModule.clear();
+  IsHeaderFile = false;
 }
 
 bool LangOptions::isNoBuiltinFunc(StringRef FuncName) const {