fix lua executables names for the regress.  The names are `luaXY` not `luaX.Y`

Index: test/cli.fnl
--- test/cli.fnl.orig
+++ test/cli.fnl
@@ -8,8 +8,9 @@
 (local test-all? (os.getenv :FNL_TESTALL)) ; set by `make testall`
 
 (local host-lua (let [long (case _VERSION
-                             "Lua 5.1" (if _G.jit :luajit :lua5.1)
-                             _ (.. :lua (_VERSION:sub 5)))
+                             "Lua 5.1" (if _G.jit :luajit51 :lua51)
+			     _ (.. :lua (-> (_VERSION:sub 5)
+					    (string.gsub "(.%w).(%w)" "%1%2"))))
                       p (io.popen (.. long " -v"))]
                   (p:read :*all)
                   (if (p:close)
