v9.0.8: MSVC compilation, github testing

This release merges a patch from @cmacdonald and crew to make compilation on Windows easier, and also adds a Github task to test compilation on Windows, Linux, and macOS.

trec_eval v9.0.7

This release rolls up some recent compilation issues. Tested on macOS Mojave (clang 11.0.0) and Ubuntu 18.04.3 (gcc 7.4).

trec_eval v9.0.6

This release rolls up the past couple patches, which address compilation issues on Linux with recent versions of gcc, and also on Cygwin. Please note that we do not test on Cygwin, we generally don't do any Windows development.

v9.0.5

No major changes, but updates to the Windows/Cygwin compile, thanks to Craig Macdonald of U.Glasgow.