[pdal] MSVC 2015+

[Howard Butler]

All,

At the OSGeo Paris Sprint, we have been discussing the Windows build situation for PDAL, and I'd like to gauge the interest in maintaining any Windows compilers less than 2015. AppVeyor supports 2015, and the proposal is we would default to building and running the tests with that platform. Though this might mostly be for Brad, I'd like everyone to have an opportunity to let us know which Windows compilers need to be supported by the PDAL team. No PDAL dev is really a full-time Windows developer at this time, but we would commit to keeping AppVeyor happy.

In short, here's your chance to stand up and say you need an older MSVC compiler supported, and if so, step forward to volunteer to do so :)

Howard