NEWS: ML platform via system options

[Makarius]

*** System ***

* The traditional ML system settings have been reconsidered, and mostly
replaced by ML_Settings in Isabelle/Scala (e.g. via
ML_Settings.system(Options.init())). Potential INCOMPATIBILITY for old
shell scripts, which should be replaced by proper Isabelle/Scala tools
anyway. The following environment variables still have a purpose:

   - ML_SYSTEM, ML_PLATFORM, ML_HOME as provided to Isabelle/ML (see also
     structure ML_System).

   - Optional ML_PLATFORM or ML_OPTIONS as input in user settings, which
     take precedence if assigned to a proper value. Otherwise,
     ML_PLATFORM is derived from system options ML_system_64 and
     ML_system_apple, and ML_OPTIONS is taken from ML_OPTIONS32 or
     ML_OPTIONS64 (depending on the effective ML_PLATFORM).

Examples:

     isabelle build -o ML_system_64 -b HOL
     isabelle jedit -o ML_system_64

* System option "ML_platform" specifies the underlying Poly/ML platform
identifier explicitly: it takes precedence over all other options and
settings to determine the ML_PLATFORM (see above).


This refers to Isabelle/d8986d88295e.


	Makarius