TODO list for typehinting branch.
Below list contains things that should be changed/fixed/implemented.


1. The debug_backtrace() does not show information about arrays type.
 * This is caused by ph7_context_new_array() creating a generic array w/o data type set.
   Most probably more builtin functions returning an array are affected.

2. PH7_OP_LOAD_IDX needs some more tweaks.