Memory leak _is_relaxation()

[jmantysalo]

src/sage/matroids/basis_matroid.pyx has _is_relaxation() with bitset_init for bb_comp and b2, but no corresponding bitset_free. Try this:

from sage.matroids.advanced import *
import gc

i = 0
while True:
    if i%5000==0:
        gc.collect() 
        print get_memory_usage()
    i += 1
    M = BasisMatroid(matroids.named_matroids.NonFano())
    N = BasisMatroid(matroids.named_matroids.Fano())
    m = {e:e for e in M.groundset()}
    tm=M._is_relaxation(N, m)
    tn=N._is_relaxation(M, m)

[dimpase]

this was easy

[jmantysalo]

Thanks. Please fill author name and put to needs_review.

If this was too easy, see psi(0.5) at #19363...

[jmantysalo]

Thanks.