Coerce does not seem to work with variable assignment

[ankrgyl]

qs> let foo int = 3::int;
qs> foo;
3
qs> let bar bigint = foo;
<qs>: error: Compiler error: Type mismatch: found Int32 not Int64

[ankrgyl]

I suspect it's the same bug, but we should also support this assigning literal values with coercion:

qs> let baz int = 3;
<qs>: error: Compiler error: Type mismatch: found Int64 not Int32