Compound resources

[pschachte]

Allow resources to be defined as the union of other resources. Using those resources then specifies that all the constituent resources are actually used. This gives a more concise syntax for specifying use of a collection of resources.

[pschachte]

Closes #46

[jimbxb]

This program

resource foo = bar

pass

compiles with no error, but it ought to be erroneous as the bar resource is undefined.

[pschachte]

OK, I think all issues have been addressed.

[jimbxb]

Yes, looks good.

Though, a test case with a compound resource in a use block would be useful.

resource foo = bar, baz
resource bar:int = 1
resource baz:int

use foo in {
    ?baz = 1
    !use_baz
    !use_foo
    !use_bar
}

def use_foo use !foo, !io {
    !println("$bar, $baz")
    ?bar = 10
}
def use_bar use bar, !io {
    !println(bar)
}
def use_baz use baz, !io {
    !printin(baz)
}