On macOS, 'Command-Left/Right Arrow' are the common shortcuts to move
the insertion point to the beginning/end of line.

See https://support.apple.com/en-us/HT201236, 'Document shortcuts'
section.

Considering that Emacs is the text editor (mostly), lets make it behave
more like TextEdit.app and not like Terminal.app about those shortcuts.

Patch attached.

Thanks!