Make the "install schema" tables follow the same table style we use

elsewhere (lines between columns).

Doc/inst/inst.tex

@@ -339,7 +339,7 @@ section~\ref{custom-install} on custom installations.
 % macro.  Uh-oh.
 
 \newcommand{\installscheme}[8]
-  {\begin{tableiii}{lll}{textrm}
+  {\begin{tableiii}{l|l|l}{textrm}
           {Type of file}
           {Installation Directory}
           {Override option}