Fixing compilation warnings

[0joshuaolson1]

"[OpenVDB c]ode must compile without any warning messages."

I haven't pared down/read much of the log, but I know there are performance warnings, possible divides by zero, and possible conversion data losses. I wonder if any of them are harmless but can't be proven to the compiler, and I haven't investigated whether the Unix-like builds encounter/suppress them with preprocessor directives or whatever.

Do you think the "dll-interface" junk comes from how the build is configured or the dynamic tbb linking?

[caron]

I honestly have no clue were those come from... I am a newb.

[0joshuaolson1]

I'll work on the unit test crashes first.

[caron]

That would be great, thanks!