Update portability information for the spawn*() functions and related constants.  Someone will need to fill in information on the spawn*() functions that aren't listed.
Update portability information for the spawn*() functions and related
constants.  Someone will need to fill in information on the spawn*()
functions that aren't listed.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator