PR10828: Produce a warning when a no-arguments function is declared in block
scope, when no other indication is provided that the user intended to declare a
function rather than a variable.

Remove some false positives from the existing 'parentheses disambiguated as a
function' warning by suppressing it when the declaration is marked as 'typedef'
or 'extern'.

Add a new warning group -Wvexing-parse containing both of these warnings.

The new warning is enabled by default; despite a number of false positives (and
one bug) in clang's test-suite, I have only found genuine bugs with it when
running it over a significant quantity of real C++ code.

llvm-svn: 147599
diff --git a/clang/test/SemaTemplate/class-template-ctor-initializer.cpp b/clang/test/SemaTemplate/class-template-ctor-initializer.cpp
index 81a5e2b..44bb4bd 100644
--- a/clang/test/SemaTemplate/class-template-ctor-initializer.cpp
+++ b/clang/test/SemaTemplate/class-template-ctor-initializer.cpp
@@ -49,7 +49,7 @@
   int
   main (void)
   {
-    Final final();
+    Final final;
     return 0;
   }
 }