QNX 7: Improvements for time measurement

Improved performance for time measurement on QNX 7.0. Closes #21 (closed)

Non-Breaking Changes

• core-module:
  • Evaluation of current system time is now shifted from Time to PlatformHelpers to allow OS-dependent code. For QNX now the (synchronized) ClockCycles() is used for high-precision timing. Through a combination with the (lower-resolution) CLOCK_REALTIME it is now possible to obtain a high-precision absolute system time (Unix Epoch).
  • Time::sleep now uses PlatformHelper::waitFor() internally
• cmake:
  • Replaced QNX 6.60 toolchain file with QNX 7.0 toolchain file (google-test still needs adaption to work on QNX)

Breaking Changes

• core module:
  • Time::currentTime() and Time::evaluateClockResolution() now always use CLOCK_REALTIME (no parameter for clock source anymore)