(1) select "System" from the main system menu or toolbar,
(2) select "Preferences",
(3) select "Keyboard Shortcuts";
(4) herein, click the "Add" button, a dialogue box apears;
(5) in the "name" field type a name for this function, such as "CTRL+Q Quit Shortcut Disabled";
(6) in the command box below the name box, enter "/bin/false" (no spaces, caps, or punctuation, i.e. don't use the quotes),
(7) click the "apply" button of this dialogue, the box will close;
(8) back in the keyboard shortcuts box, the result will appear under "customer shortcuts", click on this and while it's highlighted,
(9) push the "CTRL" key, hold it, and subsequently the "Q" key, while still holding the CTRL key; release the key combination (i.e. lift your fingers);
The line under custom command should show the name you gave it, and under the shortcust column show "Ctrl+Q".
(10) Close the "Keyboard Shortcuts" utility; pushing Ctrl+Q should no longer terminate any program that respects the universal preferences as specified by the Keyboard Shortcuts utility; on my system Firefox also obeys.