Add a PSR-4 loading script to allow Smarty to be used without Composer

[scottchiefbaker]

This is to help address #999. I created a fake "class" script that acts as a PSR-4 loading script. For Smarty 3.x and 4.x I would instantiate Smarty with:

require("include/smarty/libs/Smarty.class.php");
$smarty = new Smarty();

With this new script I can instantiate Smarty 5.x with:

require("include/smarty/src/Smarty.class.php");
$smarty = new Smarty\Smarty();

This should help backwards compatible usability for old users like me. It'd be great if this script could live in /libs/ to be 99% backwards compatible, but that directory doesn't exist anymore.

[scottchiefbaker]

Would you consider letting me recreate the /libs/ directory and putting this file in there? That would make this almost a drop in replacement for Smart 3.x and 4.x for us non-composer users. Then the only difference would be:

$smarty = new Smarty(); // Smarty 3.x and 4.x

// Versus

$smarty = new Smarty\Smarty(); // Smarty 5.x

[wisskid]

Yes, that seems fine!

[scottchiefbaker]

Excellent. I recreated the libs/ folder and put the PSR-4 file in there. I've tested the changes and everything seems to be working now.

[scottchiefbaker]

PR updated with your requested fixes.

[scottchiefbaker]

@wisskid do you need anything else from me on this?

[wisskid]

@scottchiefbaker this has been merged (with a changelog) as #1019. Thanks!