Fix those scary SystemErrors we see in DS

As it turns out, my old OnServerInitComplete fix didn't check to see if
the script had an OnServerInitComplete method. So, when we called that
method-of-doom from C++, we'd see a SystemError. Aside from removing an
error message, this probably has no effect.
Merge pull request #233 from Hoikas/py_system_error

Fix Scary SystemErrors
Merge pull request #234 from Hoikas/sdl-isused

pySimpleStateVariable IsUsed Binding
Merge pull request #230 from Hoikas/physx

PhysX Cleanup (forward port from OU)
Fix Cloth Links

A typo introduced in 49dfb4e5 caused camera stacks in AgeLink nodes to
overwrite spawn point names. This broke shell and journey cloth links in
the Relto bookshelf.
Fix crash in PtGetCameraNumber()
Use plString in PtGetCameraNumber()
Merge pull request #240 from Hoikas/fix-typo

Fix Cloth Links
Merge pull request #241 from Hoikas/camstack

PtGetCameraNumber() fixes
Window shouldn't have a resizing border.

This removes the WS_THICKFRAME & WS_MAXIMIZEBOX window styles in windowed mode.
Merge pull request #242 from cwalther/window-size

Window shouldn't have a resizing border
Merge pull request #238 from Hoikas/hdr-work

More Header Cleanups
Move file stuff back to plFile for gcc.
Merge pull request #246 from dpogue/plfile

Move file stuff back to plFile for gcc/clang.
Add UnicodeBuffer as first class data type and allow plStrings to be constructed with it
Clean up some useless junk from plString
Use plString in plConfigInfo and friends
Remove xtl::istring and xtl::iwstring
Remove an unnecessary extra heap allocation in plString::Format
Replace xtl::delete_ptr functor with lambdas