CLI: given the name of a .tst file, call Test on it

... instead of Read / READ_NORECOVERY. This is purely a convenience
feature: now one can for example run

    gap tst/testinstall/perm.tst

which is equivalent to

    gap -c 'Test("tst/testinstall/perm.tst");'

but shorter and easier to enter via shell command completion.

lib/init.g

@@ -937,6 +937,9 @@ InstallAndCallPostRestore( function()
         f := GAPInfo.InitFiles[i];
         if IsRecord(f) then
             status := READ_NORECOVERY(InputTextString(f.command));
+        elif EndsWith(f, ".tst") then
+            Test(f);
+            status := true;
         else
             status := READ_NORECOVERY(f);
         fi;