Allow for foreign proc def to alias the underlying foreign proc

[jimbxb]

Following from #366.

Currently in the stdlib, most of the Wybe procs that simply call a foreign proc could use the def foreign lang syntax. However, as the proc they call has a different name, the syntax sugar can't be applied.

As a proposal, an extended syntax sugar could be like the following:

def foreign lang foo=bar(args)

This would compile as

def foo(args) {
    foreign lang bar(args)
}

Of course, proc modifiers and the resource use clause should be optional.

[pschachte]

The proposed syntax could be confused with defining = as a foreign proc. I guess that's tolerable, since it's easy enough to write out the definition of = as a call to the foreign proc it's meant to be an alias for.