[appveyor] bump vs version, use preinstalled boost

[jgrewe]

[codecov[bot]]

Codecov Report

Merging #842 (1131b62) into master (e2b166b) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 1131b62 differs from pull request most recent head e06e9b7. Consider uploading reports for the commit e06e9b7 to get more accurate results

@@           Coverage Diff           @@
##           master     #842   +/-   ##
=======================================
  Coverage   95.33%   95.33%           
=======================================
  Files         181      181           
  Lines       13605    13605           
=======================================
  Hits        12970    12970           
  Misses        635      635           

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