Add use statements

[hamzaremmal]

This statements can be seen as import statements in other programming languages.

• To use a module in another module, we will need to add a use statement. To use Std.amy, we will need to add the following statement in our module definition

object Foo
    use Std
   // other definitions and/or expression
end Foo

• To use a single definition from a given module, you will have to use the given syntax

object Foo
    use printString from Std
   // other definitions and/or expression
end Foo

• To use a single definition from a given module with an alias, you will have to use the given syntax

object Foo
    use printString as print from Std
   // other definitions and/or expression
end Foo