Timer Initialization and Accuracy Fix

[RobertBColton]

The generalization of the main loop for SDL introduced a regression I finally caught reviewing my benchmark in #1289. The timing variables should be initialized just before input and before ANY user events (e.g, game start, room start, or the create event in my case) are fired at all, otherwise get_timer is completely inaccurate.

This occurred on Win32 where we don't query whether to use the high quality performance counter until the timing is initialized. All of the microsecond times I reported in my benchmark for #1289 are basically inaccurate to within 1/1000th of a microsecond. I am going to have to redo the entire benchmark now with this patch to see the actual difference.

I caught the mistake by wondering why none of my changes to the new model creation (in an effort to speed it up again) were affecting the results at all. I continued moving the get_timer lower and lower until I was timing the creation of a single slice of cubes. It was then reporting 0 or 15,000, but nothing in between. With this fix applied it is very very accurate and always reports differences of a microsecond or two.

Benchmark Update

Because of this issue, I decided I must record the model creation times from the benchmark in #1289 again. The results I am going to share here are relative to that pull request, not this one, because I did a hard reset and retroactively applied this patch. I record for each system the best time out of three tries.

The results basically indicate that, yeah, #1289 did generally increase the create time despite the other advantages. But with this PR going forward, I can accurately measure any optimizations I make to speed the model creation back up again. I can't do that without this change.

Branch	Create time PR (µs)	Create time Master (µs)
ENIGMA GL1	113138	71770
ENIGMA GL3	113388	77767
ENIGMA DX9	116423	70992

[codecov]

Codecov Report

Merging #1356 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1356   +/-   ##
=======================================
  Coverage   15.46%   15.46%           
=======================================
  Files         167      167           
  Lines       17386    17386           
=======================================
  Hits         2688     2688           
  Misses      14698    14698

Impacted Files	Coverage Δ
ENIGMAsystem/SHELL/Platforms/General/PFmain.cpp	81.81% <100%> (ø)	⬆️

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