Merge topic 'msvc-isystem'

f29e1874ad Compiler/MSVC: use the `-external:I` flag for system includes
5a5c85dffd Tests/IncludeDirectories: support MSVC in system include tests
399a3204bb Tests/IncludeDirectories: align sibling predicates
20ab49193b Tests/IncludeDirectories: factor out applying flags to targets
809f7b0c3a Tests/IncludeDirectories: fix copy pasta for otherlib
b094324948 Tests/IncludeDirectories: Include system headers via angle brackets
8f63f3b04e cmVisualStudio10TargetGenerator: remove unused variable

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Julien Waechter <greenjava@gmail.com>
Acked-by: DE-VS wenglor <devs.wenglor@gmail.com>
Merge-request: !4766