Improve merging of function declarations. Specifically:

  - When we are declaring a function in local scope, we can merge with
    a visible declaration from an outer scope if that declaration
    refers to an entity with linkage. This behavior now works in C++
    and properly ignores entities without linkage.
  - Diagnose the use of "static" on a function declaration in local
    scope.
  - Diagnose the declaration of a static function after a non-static
    declaration of the same function.
  - Propagate the storage specifier to a function declaration from a
    prior declaration (PR3425)
  - Don't name-mangle "main"



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@65360 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index f760852..79c51ac 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -255,6 +255,11 @@
   return 0;
 }
 
+bool FunctionDecl::isMain() const {
+  return getDeclContext()->getLookupContext()->isTranslationUnit() &&
+    getIdentifier() && getIdentifier()->isStr("main");
+}
+
 /// \brief Returns a value indicating whether this function
 /// corresponds to a builtin function.
 ///