Redundancy removal with LU if no solver is specified

[blegat]

If no solver is provided, we fall back to a representation conversion:

Polyhedra.jl/src/redundancy.jl

Lines 106 to 112 in 3e5e934

	if solver === nothing
	@warn("""
	`remove$(v)redundancy!` will trigger the computation of the $V-representation, which
	is computationally demanding because no solver was provided to the library.
	If this is expected, call `compute$(h)rep!` explicitely before calling this
	function to remove this warning.
	""" * NO_SOLVER_HELP)

We should use a LU decomposition instead