introduce array_multisort1, ..., array_multisort9
Summary:
As we are on the final stages of removing references support from HHVM, we need an alternative solutions for builtin functions, that take optional reference parameters.
array_multisort originally relied on variadic reference parameters, which are no longer supported. For now, make newly added `array_multisortN()` take arguments by reference, but I'll switch them to inout parameters as soon as inout is fully supported for builtins.
Reviewed By: billf
Differential Revision:
D16634056
fbshipit-source-id:
6100c6c9a475549633e7aa128760e084196135de