HaikuDepot TextView: add support for hyperlinks/clikable areas

Specific text spans can be assigned a cursor and BMessage to send when
they are clicked. This allows for implementing hyperlinks, specific
popup menus, and clickable text of any type.

With some extra work it can also be used to implement spell checking
suggestions, buttons, and so on.

Change-Id: I390e0c44656da76a950c432bdd934bd51af49baf
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7130
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

HaikuDepot: Fix another instance of std::remove.

HaikuDepot: Fix usage of std::remove.

That's right kids, std::remove doesn't (and can't) actually remove
things from containers! Instead you have to pass its results into
container::erase in order to do anything at all.

Fixes #17579, and in my testing at least, the strange crashes
and heap corruptions.

HaikuDepot: Remove Custom List

Closes #15534

Change-Id: I23fa60145607c3e8f25552f24c5e2c630b940537
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3758
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

HaikuDepot: Remove Custom List

Further removal of the use of custom list class;
this time part of the test engine inside HD.

Relates To #15534

Change-Id: Ia1f1d7c2577f92bba96da392fd48949a13b5a169
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3745
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

use .IsSet() instead if .Get() != NULL

Change-Id: Ia2b7a719fd398e78cc3b11d4f7b02cb81179f65f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3488
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

TextDocument: Extended comment in _Insert().

TextDocument: Change _Insert() to use TextDocument

In preparation for implementing Undo/Redo support, we need _Insert() to
take a TextDocument instead of a BString, CharacterStyle and ParagraphStyle.
When a chunk of the TextDocument has been removed, we need to be able to
Insert() that as part of the Undo operation. Not well tested, but typing
still works.

Text frame work: Implement sending TextChangedEvents

TextDocument:
* Moved implementation of Remove() and Insert() into private methods.
* Reimplement all public Insert() methods and Remove() on top of Replace().
* In Replace(), send a TextChangedEvent. Added TODO for sending a
TextChangingEvent, although at this point, I am not sure if it will be
needed at all.

HaikuDepot: Clean up trailing whitespace.

HaikuDepot: Added UndoableEditListener list to TextDocument

This is all work in progress. The plan is to move the code that does any
actual changes to the TextDocument into UndoableEdit implementations, then
emit these edits to interesed listeners. They can then store them to
implement the edit history. If there are not listeners, the edits will
simply be released after they've done their work.
Implemented so far is only the support for storing the edit listeners.

Renamed HaikuDepot's home to haikudepot.

* This closes #10699. I mentioned that to stippi after his first commit
of HaikuDepot, anyway :-)

TextDocument: Extended comment in _Insert().

TextDocument: Change _Insert() to use TextDocument

In preparation for implementing Undo/Redo support, we need _Insert() to
take a TextDocument instead of a BString, CharacterStyle and ParagraphStyle.
When a chunk of the TextDocument has been removed, we need to be able to
Insert() that as part of the Undo operation. Not well tested, but typing
still works.

Text frame work: Implement sending TextChangedEvents

TextDocument:
* Moved implementation of Remove() and Insert() into private methods.
* Reimplement all public Insert() methods and Remove() on top of Replace().
* In Replace(), send a TextChangedEvent. Added TODO for sending a
TextChangingEvent, although at this point, I am not sure if it will be
needed at all.

HaikuDepot: Clean up trailing whitespace.

HaikuDepot: Added UndoableEditListener list to TextDocument

This is all work in progress. The plan is to move the code that does any
actual changes to the TextDocument into UndoableEdit implementations, then
emit these edits to interesed listeners. They can then store them to
implement the edit history. If there are not listeners, the edits will
simply be released after they've done their work.
Implemented so far is only the support for storing the edit listeners.

Renamed HaikuDepot's home to haikudepot.

* This closes #10699. I mentioned that to stippi after his first commit
of HaikuDepot, anyway :-)