Twiggy compiler fixes

[jcheron]

• bug fix : no open issue
• BC break

Fixed:

These behaviors may have been voluntary choices...
I don't know

raw filter

Twig raw filter is not interpreted.

Twig	Expected Latte	Actual Latte
{{foo|raw}}	{$foo|noescape}	{$foo}

see 7aaba40

Twig array access

Access to the element of a Twig array is transformed into access to the member of an object.

Twig	Expected Latte	Actual Latte
{{bar['foo']}}	{$bar['foo']}	{$bar->foo}

see 209d1fb

Twig and Twiggy coexisting

pb with Twig already installed in a project (cannot redeclare Twig global functions...)

• checks with function_exists the previous declaration of the Twig global functions, see c1a06ed

_self replacement with toString

Replacing {{_self}} with {$_self} is problematic:

• _self with Twig refers to the template instance, using it alone in an expression calls the toString which displays the template name.
• $_self is not defined with Latte

Twig	Expected Latte	Actual Latte
{{_self}}	{$this->getName()}	{$_self}

see 5250d9c

Unit tests

The unit tests have been modified accordingly: see 4a2e2f5