Using platform.h instead of system headers

This way all the logic for deciding which headers need to be called is
kept inside platform.h.
Merge pull request #675 from cduclos/master

platform.h instead of system headers for HPUX
Set of fixes to logging.
  - Fix setting debug level in options.
  - General standardization of logging
Bring master ChangeLog up to speed wrt 3.4 fixes
Fix MinGW build for output review
Add function categories

This is for output in cf-promises --syntax-description for automatic categorization
of functions for documentation.
Rename ScopeDeleteSpecialScalar -> ScopeDeleteSpecial
Remove ScopeNewScalar, convert to EvalContextVariablePut
Remove ScopeNewList, convert to EvalContextVariablePut
Combine ScopeNewSpecialScalar, ScopeNewSpecialList -> ScopeNewSpecial