time related functions - implementation cleanup

[dwrobel]

time related functions - implementation cleanup

 - introduces the new common implementation of time-related functions
   for all platforms supporting c++11,
 - try to synchronize legacy (non c++11) time implementations,
 - fixes legacy (non c++11) implementation of pxSleepMS(),
 - introduces new: void pxSleepUS(uint64_t usToSleep); function,

 - fixes pxTimerNativeTest failure:
    /Users/travis/build/pxscene/pxCore/tests/pxScene2d/test_pxTimerNative.cpp:37: Failure
    Value of: (int)(endTime - startTime) == TEST_TIME
      Actual: false
    Expected: true
    [  FAILED  ] pxTimerNativeTest.pxTimerNativeTestS (2000 ms),

 - start using pxSleep*() in wayland_egl/pxWindowNative.cpp backend,

 - even pacing on wayland_egl backend.

[codecov]

Codecov Report

Merging #983 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #983      +/-   ##
==========================================
+ Coverage    62.5%   62.53%   +0.03%     
==========================================
  Files         128      127       -1     
  Lines       17927    17920       -7     
==========================================
+ Hits        11206    11207       +1     
+ Misses       6721     6713       -8

Impacted Files	Coverage Δ
src/pxTimer.h	100% <100%> (ø)
examples/pxScene2d/src/pxResource.cpp	81.25% <0%> (-0.25%)	⬇️
examples/pxScene2d/src/pxScene2d.cpp	70.7% <0%> (ø)	⬆️
src/rtFileDownloader.cpp	71.98% <0%> (+0.35%)	⬆️
src/rtHttpCache.cpp	53.58% <0%> (+2%)	⬆️

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[mfiess]

Let's leave the original file unmodified, but we can have a cmake option to using the new C++11 syntax (chrono) if configured. Otherwise we use the current files (as is). We can discuss in our next meeting.

[mfiess]

Let's leave the original file unmodified, but we can have a cmake option to using the new C++11 syntax (chrono) if configured. Otherwise we use the current files (as is). We can discuss in our next meeting.