Replacing C-style typedefs with aliases.

[datumbox]

Minor refactoring to replace typedefs with C++11 aliases.

[codecov]

Codecov Report

Merging #2945 into master will decrease coverage by 4.62%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2945      +/-   ##
==========================================
- Coverage   73.41%   68.78%   -4.63%     
==========================================
  Files          99       99              
  Lines        8801     8800       -1     
  Branches     1389     1389              
==========================================
- Hits         6461     6053     -408     
- Misses       1915     2318     +403     
- Partials      425      429       +4     

Impacted Files	Coverage Δ
torchvision/models/quantization/utils.py	16.00% <0.00%> (-72.00%)	⬇️
torchvision/models/quantization/resnet.py	28.08% <0.00%> (-65.17%)	⬇️
torchvision/datasets/cityscapes.py	20.98% <0.00%> (-59.26%)	⬇️
torchvision/models/quantization/shufflenetv2.py	34.42% <0.00%> (-55.74%)	⬇️
torchvision/models/quantization/mobilenet.py	32.65% <0.00%> (-55.11%)	⬇️
torchvision/io/__init__.py	44.82% <0.00%> (-44.83%)	⬇️
torchvision/models/quantization/googlenet.py	28.08% <0.00%> (-37.08%)	⬇️
torchvision/ops/_register_onnx_ops.py	48.78% <0.00%> (-36.59%)	⬇️
torchvision/models/detection/transform.py	78.33% <0.00%> (-17.23%)	⬇️
torchvision/io/_video_opt.py	23.42% <0.00%> (-17.15%)	⬇️
... and 13 more

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[vfdev-5]

Looks good ! Thanks @datumbox

Ref: https://en.cppreference.com/w/cpp/language/type_alias

[fmassa]

Thanks!