Doc: do not compress .epub for dist, it is already zipped.
undefine SET_SYS_FROM_STRING_BORROW after its done being used (closes #21089)
Issue 21014:  Use booleans instead of 0 and 1 in examples.
Issue #19697: Document cases where __main__.__spec__ is None.
Fix another old mention of "Standard Edition" VS in PCbuild/readme.txt.

Also removes a mention of using "Express Edition with the Windows SDK
64-bit compilers" to build 64-bit Python.  If that can be made to work,
it will need some extra instructions somewhere.
Issue #19697: document more __main__.__spec__ quirks