Track whether braces were present in T_DollarBraced

References of the form $var and ${var} both map to the same structure in
the AST, which prevents any later analysis functions from distinguishing
them.  In preparation for adding checks that need this info, add a Bool
to T_DollarBraced that tracks whether the braces were seen at parsing
time and update all references so that this change is a no-op.

src/ShellCheck/Checks/ShellSupport.hs

@@ -232,7 +232,7 @@ checkBashisms = ForShell [Sh, Dash] $ \t -> do
     bashism t@(TA_Variable id str _) | isBashVariable str =
         warnMsg id $ str ++ " is"
 
-    bashism t@(T_DollarBraced id token) = do
+    bashism t@(T_DollarBraced id _ token) = do
         mapM_ check expansion
         when (isBashVariable var) $
                     warnMsg id $ var ++ " is"