Clarify that on some systems, lockf() using LOCK_EX requires that the file is opened for writing; this closes SF bug #485342.
Clarify that on some systems, lockf() using LOCK_EX requires that the file
is opened for writing; this closes SF bug #485342.

Added notes that file objects are also accepted in the place of file
descriptors.

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