Specifying both a constraint expression and initializer in a field

[Jose E. Marchesi]

Hi people!

I just pushed a fix to both master and maint/poke-1 in order to support
specifying both a constraint expression and a field initializer in the
same field.

Example:

type Foo = struct { byte a = 10 : a in [10, 20, 30]; };

They can be also specified in another order:

type Foo = struct { byte a : a in [10, 20, 30] = 10; };

If only an initializer is specified but not a constraint, then an
implicit constraint is built fromt he initializer, like before.

Salud!