Add another try/except PermissionError to avoid depending on listdir order. Fix issues #24120 and #26012. (Merge 3.4->3.5)

Add another try/except PermissionError to avoid depending on listdir order. Fix issues #24120 and #26012.

Patch by Davin Potts and Camilla Montonen.

Issue16544 - Add a link to an external documentation resource in ast module docs.

Issue #26012: Don't traverse into symlinks for ** pattern in pathlib.Path.[r]glob(). (Merge 3.4->3.5)

Issue24898 - Improve str.find documentation.

Simplify str.find explaination as per Georg Brandl's suggestion.

Simplify str.find explaination as per Georg Brandl's suggestion.

Issue21221 - Explain the usage of tm_isdst attribute of mktime, with valid
values and meaning.

Patch contributed by Andrew Scheller.

values and meaning.

Patch contributed by Andrew Scheller.

This restores backward compatibility lost in the fix for #21075, and
is better duck typing.

Patch by Akira Li.

Issue25917 : Fix howto links in docs. Point the reference documentation instead of wiki.

Davis reviewing code.

Reported by Anatoly Techtonik on docs@