- Simplify the usage of the PUPDATE_PROGRESS callback.
- Add the possibility of specifying an initial non-zero StepCount when
creating the progress-bar (using the -Ex version), so that it can be
initially drawn with the expected initial count.
Of course ProgressSetStepCount() can continue to be used.
Improve the progress bar functions:
- Add a member in the struct, which will be used as a bar colour parameter for the new CreateProgressBarEx().
- CreateProgressBar() which will now invoke the Ex variant without the additional parameter.
