Deprecation warnings for C-style for loops

Warns of deprecation, checks all the appropriate bits to see if we can
do an automatic fix, and generates fix-its if that is valid.

Also adds a note if the loop looks like it ought to be a simple
for-each, but really isn’t because the loop var is modified inside the
loop.

include/swift/AST/Stmt.h

@@ -800,6 +800,9 @@ public:
   
   SourceLoc getStartLoc() const { return getLabelLocOrKeywordLoc(ForLoc); }
   SourceLoc getEndLoc() const { return Body->getEndLoc(); }
+
+  SourceLoc getFirstSemicolonLoc() const { return Semi1Loc; }
+  SourceLoc getSecondSemicolonLoc() const { return Semi2Loc; }
   
   NullablePtr<Expr> getInitializer() const { return Initializer; }
   void setInitializer(Expr *V) { Initializer = V; }