Change in internal call_user_function() API.

Hi, PHP-7.0 internal call_user_function() API doesn't support function calls with preinitialised symbol tables. This just can't work in general , because values of arguments might be already initialized in CV as well as in symbol table. I propose to remove the corresponding internal API in master: 1) remove last argument of call_user_function_ex() 2) remove zend_call_info.symbol_table field https://gist.github.com/dstogov/5550827aa695ff8cb803 The tricky way was used in phpdbg only, but that code doesn't work, and should be fixed anyway. Thanks. Dmitry.