In a `MonotoneFramework` it is sometimes necessary to change the
information propagated on a branch w.r.t. another branch.

This commit introduces the `handleEdge` function that allows
`MonotoneFramework` implementors to modify the `LatticeElement` produced
by `transfer`.

`dumpModule` is a debug function that can be called from GDB to dump a
`Module *` to a chosen path.

`MonotoneFramework.h` has been moved into `include/revng/Support` so
that it can be employed by components outside `libStackAnalysis`.

In stack analysis' output, the list of basic blocks composing a function
was not sorted. This lead a test to fail due to the presence of the
`--order` flag when comparing the output.

This commit ensures that this list is ordered, by basic block name.

This commit dismisses the `argparse` library (the only non-runtime C
component of rev.ng) in favor of LLVM's CommandLine library, which
offers several benefits. Among others, now command line arguments can be
easily specified as a global variable, decentralizing their management
and avoiding the long list of arguments in the constructor of singleton
objects such as `CodeGenerator`.

This commit introduces `revng_log`, a macro analagous to `revng_assert`,
which basically allows to have the benefit of the `Logger` class without
having to compute the expression to log if the logger is disabled.

This commit also completely dismisses the `DBG` macro, converting all
the old code to `Logger` + `revng_log`.

This commit moves around most files. The new directory structure is as
follows:

* `lib/$LIBRARY/`: contains a library, i.e., a set of `.cpp` files used
  by multiple libraries/tools.
* `include/revng/$LIBRARY/`: contains the public headers associated to
  the library in `lib/$LIBRARY/`.
* `tools/$TOOL/`: directory where all the `.cpp` files (and private
  headers) for a tool reside. Currently we have two tools: `revamb` and
  `revamb-dump`.

On top of this, all file names are now in camel case.

This commit enforces on the whole project the usage of our own assertion
system. This means all calls to `abort`, `assert` and `llvm_unreachable`
have been replaced with calls to `revng_abort`, `revng_assert` and
`revng_unreachable`, respectively.

The error messages, usually expressed as `assert(Condition &&
"Message")` have now been replaced using the second (optional) argument
of `revng_assert`.

Additionally, all the `assert(false)` statements have been replaced with
calls to `revng_abort`. Apart from readibility, this ensures the
compilers is aware of the fact that call will never return.

This change will enable us to drop many statements whose sole purpose
was marking a variable employed in an assertion as used in release
mode. In fact, with the new assertion system this is no longer
necessary.

We used to have a `_` prefix for include guards macros, however,
according to the standard, macros starting with an underscore are
reserved. This commit drops them all.

This commit applies our `clang-format` rules globally. From now on, all
commits should respect our configuration file.

Pretty large change.

This commit introduces `using` statements and `constexpr` functions to
increase readibility of various types.

This commit introduces a check in `check-conventions.sh` to prevent
committing code denoted by a `// WIP` comment, that are supposed to be
used to remind the developer something has to be changed before
submitting a pull request.

This is a very large commit importing the reviewed (and heavily
simplified) stack analysis and the new ABI analysis, which provides
information on the calling convention of each function and so on.

For an overview of the new analyses please consult OVERVIEW.md.