remove order dependency between "using" and "addprocs"

The following sequence resulted in the worker segfaulting and terminating.

• using PTools
• addprocs(1)
• call a method in PTools. The method creates an anonymous function (in PTools code) and does a remotecall_fetch on worker 2 for executing the said anonymous function.
• worker 2 terminates at a deserialize call.

Flipping the order of addprocs and using results in proper execution.

Suggest that we keep track of modules loaded in process 1, and load the same modules on all workers whenever we do an addprocs

Reproduce the reported sequence involving using PTools, addprocs(1), and remotecall_fetch of an anonymous function, then compare it with the reversed order. Investigate the module-loading path around addprocs and the worker's deserialize failure; done means workers execute the call without terminating regardless of the order.