Specifically, this commit improves the stepping behavior of the IR
backend around functions with defaults.
- Improved line numbers in the default handler itself for better
stepping when inlined.
- Improved source information on default arguments
- Improved test coverage of stepping behavior in old and IR backends.
Improves the stepping behaviour around inline methods with default
arguments. In particular, we now accurately step through the
evaluation of default arguments, but do _not_ spuriously show the exit
from the $default handler.
Fix line number generation for assignments where the right-hand
side of the assignment is not on the same line.
Fix line number generation for intrinsics functions where the
function is not on the same line as the last argument.
Be careful to not break stepping behavior with the iinc
optimizations.
Kristoffer Andersen