Add BIconUtils::GetSystemIcon

Allow to easily access the alert icons and anything that's added to app_server
resources.

Fixes #10887.

Convert BAlert, Debugger AlertWithCheckbox and Keymap ModifierKeysWindow
to make use of it, removing the duplicate code to locate app_server
resources.

The resources are initialized only once (per application), so there is no need
to reload them for every access to the icons.

In the ticket there is discussion about putting this in BControlLook,
but I think this should in fact be moved fully into app_server with
special drawing commands for well-known icons. That would avoid loading
and rendering the icon on the application side to then send it to
app_server (especially in remote_app_server case)?

In any case, this simple API can serve as a base for applications to
use, and we can change how it is implemented later on.

Change-Id: Id370526ae5cf165cfb8bc277bc8a7f46c26f542d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6463
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

API docs: it's => its fix

IK documentation update

* Add \since directive to each method.
* Add documentation for BScrollBar and BScrollView classes.
* Title Case group titles.
* Some other minor documentation updates.

Big docs cleanup.

* Fixed headers including:
- All rights reserved not All Rights Reserved.
- name, email@domain.com not name <email@domain.com>
- tabs and spaces
- Authors: not Documented by:
* Renamed string.dox to String.dox
* Renamed midixxx.dox files to MidiXxx.dox
* Moved images into images subdirectories and updated Doxfile.
* Re-format all files with tabs instead of spaces.
* Fix many spelling mistakes.
* Added all files, classes, structs, and enums to libbe group.

Patch by John Scipione again : fix the new BIconUtils documentation.
thanks!


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42609 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Add the header file to doxygen, too
* Fix copypaste error.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42607 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Add BIconUtils documentation to the Haiku Book
* Remove comments from the header itself.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42606 a95241bf-73f2-0310-859d-f6bbb57e9c96

IK documentation update

* Add \since directive to each method.
* Add documentation for BScrollBar and BScrollView classes.
* Title Case group titles.
* Some other minor documentation updates.

Big docs cleanup.

* Fixed headers including:
- All rights reserved not All Rights Reserved.
- name, email@domain.com not name <email@domain.com>
- tabs and spaces
- Authors: not Documented by:
* Renamed string.dox to String.dox
* Renamed midixxx.dox files to MidiXxx.dox
* Moved images into images subdirectories and updated Doxfile.
* Re-format all files with tabs instead of spaces.
* Fix many spelling mistakes.
* Added all files, classes, structs, and enums to libbe group.

Patch by John Scipione again : fix the new BIconUtils documentation.
thanks!


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42609 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Add the header file to doxygen, too
* Fix copypaste error.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42607 a95241bf-73f2-0310-859d-f6bbb57e9c96

* Add BIconUtils documentation to the Haiku Book
* Remove comments from the header itself.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42606 a95241bf-73f2-0310-859d-f6bbb57e9c96