Add IO for loading and calling dynamically linked libraries

[developedby]

Is your feature request related to a problem? Please describe.
Hvm added dylib support in HigherOrderCO/HVM#394, but it was never added to Bend.

Describe the solution you'd like
Expose the dylib functions dl_open, dl_call, dl_close with a user friendly interface, like we did for files.

# 'path' is the path to the dl file.
# 'lazy' is a boolean encoded as a u24 that determines if all functions are loaded lazily or upfront.
# Returns an unique id to the dl object encoded as a u24
IO/DyLib/open : (path: String) -> (lazy: u24) -> u24

# Calls a function of a previously opened dylib.
# 'dl' is the id of the dl object
# 'fn' is the name of the function in the dylib
# 'args' are the arguments to the function. The expected values depend on the called function.
# The returned value is determined by the called function.
IO/DyLib/call : (dl: u24) -> (fn: String) -> (args: Any) -> Any

# Closes a previously open dylib.
# 'dl' is the id of the dylib.
# Returns nothing.
IO/DyLib/close : (dl: u24) -> None

We should also include some documentation with an example program to be compiled as a dll an loaded into bend.