Fix macro expansion of _PyErr_OCCURRED(), and make sure to use it in at least one place so as to avoid regressions.

Closes #1215: document better why it is not a good idea to catch e.g. SIGSEGV and refer to faulthandler.

Patch by Martin Pool.

Use the platform-independent way of calling a script from the shell: "python prog.py", not "prog.py"

Found by Micheal Wells on docs@.

Fix: >= and so on are usually called "comparison operators", not "logical operators". Found by Tom Kalt on docs@.

Closes #15228: remove reference to Unix "touch"; it is confusing since the path needs to exist for os.utime() to succeed

Patch by Filip Gruszczyński.