Feat spread operator for array

[alexander-akait]

• support spread operator (...) for array
• always use entry for any item in array (PHP parser do same)
• add byRef to entry node if we use & with variable to avoid invalid grammatical
• add unpack when ... uses
• tests
• remove unnecessary read_byref due refactor

Entry when key is null means value item ([$var, $var2, $var3])
Entry when key is not null means key-value item (['one' => $var, 'two' => $var, 'three' => $var])

Interesting note - grammar support ... in list and in foreach, but php throw error in runtime, we need do same in future, now it is impossible due invalid grammar in read_expr_item, we need refactor and them do it, it is not high priority because nobody writes this code

[coveralls]

Coverage increased (+0.02%) to 95.877% when pulling bf80c6f on feat-spread_operator_for_array into 0df5a49 on master.

[ichiriac]

@evilebottnawi does this branch should be merged ?

[alexander-akait]

Need review and we can merge this 😄

[ichiriac]

it's ok