Flight time debugging

Added an option to the octree servers to print out additional usecTimestampNow() debug info every 10 minutes (if requested)... this is to help track down the unreasonable flight time messages that are still happening when a server runs for over 12-20 hours.
BTW, static variables make this timeStamp implementation easy but the compiler will create a branch in the machine code for each static (basically an "if static is not initialized, then initialize it" logic block).  This makes usecTimestampNow() less efficient that it could be and thus can make it a poor choice for timing very hot loops.

I only know this because the devs at Linden Lab learned  a similar lesson when using a timer to perform microthreading yield logic in the script bytecode interpreter.