Issue #17386: List the 'htmlview' target in the Doc/Makefile help output.
Issue #17386: Update Doc/README.txt to list all targets
supported by Doc/Makefile, as well as a bit of modernization,
cleanup, and notes about the difference between Unix and Windows.
Issue #17386: Expand Doc/make.bat to be much more similar to Doc/Makefile
Closes issue #21316: mark test_devpoll to be meaningfull only for Solaris
Issue #21374: Fix pickling of DecimalTuple.
Document the subprocess Popen.args attribute (issue21353)
Document the subprocess Popen.args attribute (issue21353)