Simplification pass

[ailrst]

Adds the flag --simplify (which implies --parameter-form) which, before running analysis performs partial evaluation and simplification of the IR. To assist this it does a DSA transform, but the copy propagation which runs afterwards is going to undo this somewhat.

This usually removes the flag registers and pushes the comparisons into the assume statements where they are used, folds constants through and does some canonicalisation and term simplification.

It sits on top of the interpreter #241 for partial evaluation, and includes improvements to the parameter form which I will copy into that PR #255. When #243 is merged we should use the interpreter to validate the transform using the memory state hash the csmith examples produce. Currently this is just validated against the system tests, all of which pass with the transform applied.

this implements:

• a dsa transform via variable renaming
• constant + copy propagation over the IR
• a term-rewriting based simplification pass
• partial evaluation

The simplification/partial eval/copyprop rewrites are applied repeatedly with a fixed number of iterations.

For an example of what simplifications this produces: http://0x0.st/XE79.html

[ailrst]

This improves the DSA, and adds a check for the property. It also adds block coalescing and a debugging flag to perform procedure trimming before running the analysis (so I can test a specific function in cntlm).

This no longer adds all globals from specs to the boogie, because we can't tell if they are global or have been promoted to local. If they are referenced in spec they must be defined in the actual program, so this shouldn't matter.
Test basic_lock_security_write and basic_sec_policy_write are failing now, because the Gamma_R0 in the precondition is optimised out of the program (R0 isn't live at the stat of the program, so I suspect its miscompiled, especially given the signature int main(int secret) is undefined behaviour. basic_lock_read/clang/GTIRB is also timing out suspiciously.