fix #7739. for addprocs, this makes dir always specify the starting working directory (defaults to pwd()) and makes exename always specify the julia binary to run (defaults to $JULIA_HOME/julia)
Two improvements to FunctionMover

- Don't crash on Functions that don't have a name set
- Ask MCJIT for GlobalVariables, not the memory manager
Merge pull request #9459 from JuliaLang/jn/cluster_dir_cmd

fix #7739 (for addprocs)
update windows build instructions
more fixes for win64 stack unwind and function lookup
Use concrete typing on the indexes tuple for SubArray construction

This works around bugs due to #8504.
maybefloat & maybeint: parse string to Nullable

Introduces following methods that parse a string as the indicated type and return a `Nullable` with the result instead of throwing exception:
- `maybeint{T<:Integer}(::Type{T<:Integer},s::AbstractString)`
- `maybefloat32(s::AbstractString)` and `maybefloat64(s::AbstractString)`

Ref: discussions at #9316, #3631, #5704