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>

* 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

Moved IconUtils.h to Interface Kit and therefor made it an "official" header. Since the class has no
virtual but only static methods, it is not so likely that binary compatibility issues may arrise
from using it in new apps. Adjusted all the Jamfiles that included the private libicon headers. Note
that it was never necessary to link against libicon.a, since it's part of libbe anyway. There was one
instance where that was done. Hopefully it does not break the build, but I did this change a while ago,
tested it and then the harddrive began failing.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40679 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

Moved IconUtils.h to Interface Kit and therefor made it an "official" header. Since the class has no
virtual but only static methods, it is not so likely that binary compatibility issues may arrise
from using it in new apps. Adjusted all the Jamfiles that included the private libicon headers. Note
that it was never necessary to link against libicon.a, since it's part of libbe anyway. There was one
instance where that was done. Hopefully it does not break the build, but I did this change a while ago,
tested it and then the harddrive began failing.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40679 a95241bf-73f2-0310-859d-f6bbb57e9c96