Split isFromMainFile into two functions.

Basically, isInMainFile considers line markers, and isWrittenInMainFile
doesn't.  Distinguishing between the two is useful when dealing with
files which are preprocessed files or rewritten with -frewrite-includes
(so we don't, for example, print useless warnings).

llvm-svn: 188968
diff --git a/clang/lib/Rewrite/Frontend/RewriteModernObjC.cpp b/clang/lib/Rewrite/Frontend/RewriteModernObjC.cpp
index 546f921..80b6b41 100644
--- a/clang/lib/Rewrite/Frontend/RewriteModernObjC.cpp
+++ b/clang/lib/Rewrite/Frontend/RewriteModernObjC.cpp
@@ -791,7 +791,7 @@
     }
   }
   // If we have a decl in the main file, see if we should rewrite it.
-  if (SM->isFromMainFile(Loc))
+  if (SM->isWrittenInMainFile(Loc))
     return HandleDeclInMainFile(D);
 }