Replace getTickCount with os.clock

[qaisjp]

Is your feature request related to a problem? Please describe.
Can be related to mantis 5115.

Describe the solution you'd like

Pending merge of #316, redirect getTickCount to os.clock.

Try one of these:

• Doing an assignment using the Lua API when we create functions
• Change Luadef for getTickCount to just call os.clock (don't do this, just unclean)
• Edit autoload Lua script to say getTickCount = os.clock (maybe don't do this, C is preferred)

[ccw808]

os.clock returns seconds, so cannot be used as a drop in replacement for getTickCount

[qaisjp]

And so it is!