Speed improvement for large projects & path fixup for sln/vxproj inputs

[peitschie]

Was playing with this last week (before your email even! How coincidental!) and noticed these few small tweaks were required to get my current project going with your new and very cool vxproj integration.

A minor suggestion if you're interested, there's a lot of trailing whitespace in these files. If you're using Visual Studio, it might be worth installing https://visualstudiogallery.msdn.microsoft.com/a204e29b-1778-4dae-affd-209bea658a59 which can automatically clean this up for you on save.

[g-h-c]

Thanks for your pull request. Why to use a set rather than vector? We do not perform any searches on sysincludedirs, why does using a set make a difference?

[peitschie]

We do not perform any searches on sysincludedirs, why does using a set make a difference?

For some reason (perhaps I should dig more into why), this vector was growing very large with a lot of duplicate entries (e.g., 32,000+ system include directories!). Changing it to a set kept the performance high, purely because it avoided dupes.

So, the optimization wasn't for searching, but avoiding unnecessary copies.