Debug StepInto stops at beginning of arrow function

[tomatosalat0]

When using StepMode.Into, the debugger callback DebugHandler.Step did not get fired before the execution of a single expression arrow function.

For example, having this statement

[1, 2, 3].map(v => v * 2)

The debugger would not stop before the v * 2 expression - only after.

In contrast, having this statement

[1, 2, 3].map(function(v) { return v * 2; })

The debugger would stop before and after the return v * 2 expression.

Two tests were added, one for the function type and one for the arrow type.

[lahma]

LGTM, thank you!