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/tools/libclang/CXSourceLocation.cpp b/clang/tools/libclang/CXSourceLocation.cpp
index 71e425d..a33c9d4 100644
--- a/clang/tools/libclang/CXSourceLocation.cpp
+++ b/clang/tools/libclang/CXSourceLocation.cpp
@@ -217,7 +217,7 @@
 
   const SourceManager &SM =
     *static_cast<const SourceManager*>(location.ptr_data[0]);
-  return SM.isFromMainFile(Loc);
+  return SM.isWrittenInMainFile(Loc);
 }
 
 void clang_getExpansionLocation(CXSourceLocation location,