[Xitami] Small modification to ISAPI support

[JLIST]

Among other things, Xitami's lack of URL rewriting feature
bothers me. So I made a couple of small changes to the ISAPI
add-on, basically adding a -i/-I option to show index.dll. When
no DLL file name is given in the URL, index.dll is used instead.
This makes it possible to have URLs like http://domain/register,
instead of http://domain/isapi_exe/register.dll

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>     show_index     = FALSE;               /* Use index.dll if dll isn't in url */
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>                 case 'I':               /* Alway unload ON                   */
>                 case 'i':
>                     show_index = TRUE;      break;
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>     static char index[] = "index.dll";
> 
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> 
>     if (show_index && (!strstr(path_info, ".dll")))
>         path_info = index;