Bump up version

See merge request !9

This ensures we do not rely on a version of the library that's too old
by accident.

This change does not adhere to the Haskell package versioning policy
(see https://wiki.haskell.org/Package_versioning_policy )
so that we can mirror the original igraph library's version numbers.
This should not be a problem, because nobody is using our fork of the
library except us.

Relax dependency bounds

See merge request !8

This reverts commit 1e2b0ac7.

This reverts commit d27810f3.

Proper (and thread-safe) implementation for `withSeed`

Closes #5

See merge request !6

In order to achieve feature-parity we need to use
the same type of RNG that igraph would use for the default one,
which is PCG32.

This commit does two things:

1. It allows `withSeed` to call the given function `fun` with a new
rng (which seed has been appropriately set), but at the same time
restores the previous RNG once we finish running the action;

2. It guards the inner action via a mutex so that we can get thread
   safety. This is implemented via `withGlobalRNGLock`.

Upgrade nixpkgs and GHC

Closes #3

See merge request !5

This commit fixes the c2hs calls for the clique functions, as igraph
switched to be using a igraph_vector_int_list_t.

This commit fixes more occurrences of an `igraph_vector_t` being
erroneously used in place of a `igraph_vector_int_t`, introduced in
newer versions of `igraph`.

This commit switches to be using 0.10.4, fixing most API changes along
the way. It also stops vendoring igraph, in favour of the system
library, which now needs to be installed.