fix Issue 11789 - No setAttributes to complement getAttributes

- add std.file.setAttributes

[Issue 11789](https://d.puremagic.com/issues/show_bug.cgi?id=11789)
Merge pull request #1804 from MartinNowak/master

add std.file.setAttributes
Remove typetuple dependencies
Merge pull request #1807 from monarchdodra/typetupleImport

Remove typetuple dependencies
Disable setting thread priority
Add link to bug page
Merge pull request #1808 from mxfm/threadpriority

Disable setting thread priority in TaskPool unittest
Add import declarations for issue 313 & 314
Merge pull request #1811 from 9rnsr/fix_imports

Add import declarations for issue 313 & 314