Added support for includes and functions in cat

[ThomasHaas]

This PR is marked as DRAFT simply because there are currently no tests related this feature, and no existing .cat-files were updated. Otherwise, the PR is functional.

Added functionality:

• include "filePath" now has semantics in .cat files.
• Semantically, the included file (if it exists) is simply inlined into the including file (as if copy&pasted). If the file does not exist, we give a warning and treat it as NOOP.
• The filePath is resolved relative to an optionally provided --cat.include=<includeDirectory> which defaults to DAT3M_HOME/cat.
• Includes can be nested but there is no detection of recursive includes: those will likely cause recursion until out of memory.
• Support for functions (see below)

If anyone (@hernan-poncedeleon ? :)) is interested in rewriting existing .cat files to make use of this feature, you are welcome to add to this PR. In particular, a simple basic.cat with definitions such as let poloc = po & loc would be nice to have so that we can remove a lot of hardcoded definitions from the Wmm class.

Possible other feature: I want to take a look into adding parametric definitions as in #733 to this PR but with a less invasive approach (i.e., purely implemented in the parser).

EDIT: I implemented functions/function calls in .cat. The support is very extensive:

• Multiple parameter are allowed: let f(x, y) = x | y (though 0 parameters are currently unsupported)
• Functions also work for unary sets:

let f(x, y) = x | y
let hb = f(com, po)
let M = f(R, W) 

• Functions capture the context in which they were defined:

let z = oldDef
let f(x, y) = x | y | z // refers to the above defined z
let z = newDef
let a = f(b, c) // uses `oldDef` for z

• Functions can be redefined just like relations
• Functions can take complex arguments: let hb = f(po, f(co, f(rf, f(fr))))
• Functions can call other functions: let g(x) = f(x, x). They cannot call themselves (recursion in functions is not allowed)

[hernanponcedeleon]

If anyone (@hernan-poncedeleon ? :)) is interested in rewriting existing .cat files to make use of this feature, you are welcome to add to this PR. In particular, a simple basic.cat with definitions such as let poloc = po & loc would be nice to have so that we can remove a lot of hardcoded definitions from the Wmm class.

Do we want to keep treating ctrl, data, addr as "base" relations or should we define them as

let data = (idd^+) & (M * M)
let addr = (addrDirect | ((idd^+);addrDirect)) & (M * M)
let ctrl = ((idd^+);ctrlDirect) & (M * V)

Put it differently, do we want to get rid of all relations that make use of operators in Wmm.makePredefinedRelation()?

[ThomasHaas]

Possibly. The awkward part is that some of those base relations like idd are magical in that they argue about non-visible events. I'm not sure if we want to expose them.