define some doctestfilters

[ThomasBreuer]

... in order to avoid failures in doctests with Julia 1.6.0-DEV
(due to changed typeof outputs in Julia 1.6)

Note that doctestfilters is supported in makedocs but currently not in doctest,
therefore running doctests as a part of GAP.jl's test suite gets disabled with the proposed changes.

Perhaps there will be support also in doctest in the future, see JuliaDocs/Documenter.jl#1364.

The changes are intended to resolve issue #484 .

[codecov]

Codecov Report

Merging #491 into master will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #491      +/-   ##
==========================================
- Coverage   72.59%   72.50%   -0.10%     
==========================================
  Files          68       68              
  Lines        5211     5212       +1     
==========================================
- Hits         3783     3779       -4     
- Misses       1428     1433       +5     

Impacted Files	Coverage Δ
src/constructors.jl	95.65% <0.00%> (-4.35%)	⬇️
src/adapter.jl	86.66% <0.00%> (-3.34%)	⬇️
src/ccalls.jl	96.82% <0.00%> (-1.59%)	⬇️
src/gap_to_julia.jl	96.27% <0.00%> (-1.23%)	⬇️
test/conversion.jl	33.33% <0.00%> (ø)

[fingolfin]

Great! Hmm, perhaps we could use such a feature in GAP's Test, too... As we also have on GAP test failing:

########> Diff in /Users/travis/build/oscar-system/GAP.jl/pkg/JuliaInterface/t\
st/utils.tst:9
# Input is:
JuliaTypeInfo( GAPToJulia( JuliaEvalString( "Array{Any,1}" ), [ 1, 2, 3 ] ) );
# Expected output:
"Array{Any,1}"
# But found:
"Vector{Any}"
########
    1130 ms (334 ms GC) and 233KB allocated for utils.tst