whitespace is a substring of smallest leading whitespace.
Based on patch by Robert Li.

Clarify message and expected action for beginners.

Patch written by Bernt Røskar Brenna.

with what findCaller() does when running on non-POSIX platforms.

(alternatively: the normcase calls in both places could be eliminated, but that
touches more code and that refactoring hasn't even been done in 3 yet...)

properly to get the filename of its caller from the stack.  This allows it
to work if run in a frozen or embedded environment where the module's
.__file__ attribute does not match its code object's .co_filename.

This same much simpler always correct approach has already been deployed and
used widely in Python 3.4 per the issue referenced above.

when running the test suite.

Patch by Arfrever Frehtes Taifersar Arahesis.

tab in the IDLE Preferences dialog.  Code patch by Mark Roseman.

the other buttons and the new IDLE Dark theme.

Patch by Nir Soffer.

Also add to comment in the C code.

was locale depending.

Also change glossary heading from "view" to "dictionary view". Patch by Akira
Li.