Stack-too-deep Post-Fix

[alexcere]

With the Greedy modified, adapt last step for solving stack-too-deep errors:

• Identify elements to fix when applying the greedy algorithm.
• First pass: introduce needed VGET-VSET/DUP-VSET for phi-functions that are always inaccessible.
• Second pass: determine SET instructions to dominate GET/VGET-VSET instructions according to the
• Third pass: register colouring.