First pass over plMessage headers.

This reduces the amount of redundant #includes in the plMessage headers.
Still need to check over the actual source files and do some work to
remove pnUtils (ugh) from one message.
Fix unsafe cast
Remove unused NetCommMsg
PCH-ize plMessage
Fix fallout in 3dsm plugin
I did it wrooong
Merge pull request #391 from Mystler/fix

Fix null dereference issue
Various MinGW compile fixes.
Merge pull request #394 from dpogue/mingw-fixes

Various MinGW compile fixes.
Clean up some warnings, and make the CRT ones more relevant
Added link to Roadmap wiki page.
Fixes for semaphores on *nix.
Remove plFileSystem::GetTempFileName.

It was unused and on *nix used the deprecated mktemp function.
Fix a clang warning in plPythonPack.
Merge pull request #393 from dpogue/nix-fix

*nix fixes
Merge pull request #397 from zrax/warnings

Clean up some warnings, and make the CRT ones more relevant
Only try to find the Max SDK if it was requested (and show the option to try to build it always)
Use the UTF-8 version of Expat
Clean up plDistributor max/pl point interop

There were two terrible things here:
* Some nasty pointer-based casting
* Storing references to temporaries

Unfortunately, storing addrs of temps was happening through a helper
function, so VS won't warn here. I think I caught all the cases where
those functions were being used wrongly, but I can't be sure until
coverity runs on this commit.
Add better error handling to app.event console command