Unwanted Tooltip when going back in history with Alt+Left

If you use Alt+Left to go back in the navigation history a tooltip might be displayed if the position you get back to is inside an identifier (e.g. for the cpp editor).

1. This is probably not intended.
2. In case of the cppeditor, this makes the UI sluggish since CppHoverHandler::identifyMatch() might become quite expensive due to the calls into Core::HelpManager::linksForIdentifier().

Reproduce:

1. Open cppeditor.cpp.
2. Find the line "this, SLOT(updateSemanticInfo(CppTools::SemanticInfo)));" and position the cursor on "updateSemanticInfo".
3. Hit F2.
4. Now hit Alt+Left (and immediately the e.g. Down-Arrow to experience the sluggishness)

Actual: Tooltip is shown.
Expected: Tooltip is not shown.