Bugfix: MagicNumber with ignoreNamedArgument and a negative value

[jonasfa]

Fixes #530

[schalkms]

Thanks for this bug fix as a your first contribution!

[codecov-io]

Codecov Report

Merging #2315 into master will decrease coverage by <.01%.
The diff coverage is 50%.

@@             Coverage Diff              @@
##             master    #2315      +/-   ##
============================================
- Coverage      81.8%   81.79%   -0.01%     
- Complexity     2117     2118       +1     
============================================
  Files           348      348              
  Lines          6050     6053       +3     
  Branches       1106     1108       +2     
============================================
+ Hits           4949     4951       +2     
  Misses          518      518              
- Partials        583      584       +1

Impacted Files	Coverage Δ	Complexity Δ
...itlab/arturbosch/detekt/rules/style/MagicNumber.kt	88.6% <50%> (-0.87%)	61 <3> (+1)

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[jonasfa]

Rebased