criteria: fix issue #2157 and added tests

[maxgalbu]

See the discussion here:
http://forum.phalconphp.com/discussion/1479/multiple-joins-in-oo-notation-fail

From what I saw, the problem was that the current_joins was merged with the join array instead of appended, so it resulted in something like this:

array(
    //first join
    0 => array(
        'type' => "LEFT",
        'conditions' => "...",
    ),

    //all the following joins
    'type' => "LEFT",
    'conditions' => "...",
)

instead of

array(
    //first join
    0 => array(
        'type' => "LEFT",
        'conditions' => "...",
    ),

    //all the following joins
    1 => array(
        'type' => "LEFT",
        'conditions' => "...",
    ),
)

This is my first attempt at editing phalcon code, I have some experience with c code but none with php extension. I didn't tried but i guessed I couldn't edit current_joins directly, so phalcon_array_append is out of the question. I don't know how to copy a zval, so to avoid editing too much code I simpy added an array of array that can be merged with current_joins or copy-written on merged_joins.

[phalcon]

Hi, thanks for trying to fix this, could you please submit this to 1.3.2?

[phalcon]

Thanks

[maxgalbu]

Wait, you merged my 1.3.2 based branch on your 1.3.1 branch so some commits that were done on 1.3.2 slipped onto your 1.3.1 branch, is that what you wanted?
Sorry for that, I force-updated my branch instead of creating a new one for 1.3.2 :(

[phalcon]

No, I thought the old PR was closed and merged it :'(