[Issue 24060] New: Improve "Cannot create instance of abstract class" error

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24060

          Issue ID: 24060
           Summary: Improve "Cannot create instance of abstract class"
                    error
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: grimmaple95 at gmail.com

When you try to create an abstract class, like this:
```
import std;

abstract class A
{
    abstract void foo();
}

class B : A
{

}

void main()
{
    B b = new B();
}
```

you get this error:
```
onlineapp.d(15): Error: cannot create instance of abstract class `B`
onlineapp.d(15):        function `void foo()` is not implemented
```

Note that it points to where the class is being created (line 15), not to the
class `B` itself where the erorr happens. I think a reference to where class
`B` is defined should be added. It will be convenient for IDEs to ctrl + click
to follow where the class `B` is defined.
Also, "function `void foo()` is not implemented" should point to line 5, the
place where the abstract function is defined.

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