Procedure cloning at the strongly connected component level

[zyzek]

At present, procedures are cloned at the block level. But the current algorithm induces an infinite loop when the cfg is cyclic.

A solution: keep track of SCCs, and clone them in their entirety. In this way procedures still should get cloned without bloating up their interiors if they contain cycles, and cycles will not produce infinite clones of themselves.

Should be tackled at the same time as #22 .