Link new module summary entries to their description sections.
Collapse 'python invocation changes' into 'other improvements'.
Move other improvements and optimization sections above deprecated.

This arrangement means the sections that have summaries come
first, and everything else comes after those.
Make the 'read on' sentence cover more ground.
Mention PATHEXT and removed Misc dirs; clarify wording of a NEWS entry.
Mention Windows 2000 and OS/2 drops, python-config as shell script.
Move argument clinic into its own section, like the other PEPs.
Use endash in PEP callouts.

Despite Serhiy's suggestion in issue18529, the emdash just looks
too long to me, at least in my browser.  This usage case is sort
of halfway between endash (connective) and emdash (pause/separator).
sys.getallocatedblocks + regrtest -R, make coverage-report, SO macro goes away.
Use title case for all section titles except module names.
Move no-longer-supported operating systems into 'removed' section.
Neaten up structure of major sections.

Also move tick_counter from deprecated section to removed section.
Move IPv6 NEWS entry into correct section.
Fix English in a NEWS entry.
idle -n deprecation, fix case of pickle section.
#16832: s/integer/object/ in docs/docstring, and add whatsnew entry.
pty.spawn returns os.waitpid; optimization of BZ2File and LZMAFile.
Issue #20058: sys.stdin.readline() in IDLE now always returns only one line.
Issue #20058: sys.stdin.readline() in IDLE now always returns only one line.
Issue #19020: Tkinter now uses splitlist() instead of split() in configure
methods.