Update to reflect review feedback.

There are just three changes here:
- In chplsys.c, only define getPUsPerCore() for Linux targets, not for
  all non-Apple targets.  It's only called on Linux targets.
- Also in chplsys.c, collapse the multi-space runs into single spaces in
  the sscanf() format strings used to read values from /proc/cpuinfo.  A
  single space in the format is sufficient to match any amount of white
  space in the input, and using multi-space runs implies more input
  matching precision than is actually happening.
- Explicitly cast return values where they don't match the function
  return type, in both chplsys.c and the tasking layers.