qdoc: Simplify config code for reading file paths

This change greatly simplifies the code used for
reading paths from config files: near-identical
functions Config::getCanonicalPathList() and
Config::getPathList() are combined into one, and
the use of Config::getCleanPathList() is
replaced with the above.

Effectively, all paths read from the config files
are now converted into canonical ones.

It also adds support for absolute paths in config
files.

Task-number: QTBUG-36193
Change-Id: I2dc1ee6a67a400e056404ec1c09c6e81f643aa77
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
Add support for -qwindowicon command line argument.

[ChangeLog][QtGui][QGuiApplication] Add support for -icon command line
argument on X11, add -qwindowicon on all platforms.

Change-Id: Iacc602466699bf634d8b34aab7ed73c83fd9844f
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Factor xcb check into a local variable

Change-Id: Ib57f73f7a733a94bed4522ddd2d19c4980d8d6b6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
QtGui: Use Q_REQUIRED_RESULT in many more places

gcc doesn't yet warn when a non-POD return datatype is unused,
but clang does, at least.

Change-Id: Ia4c39001994ac09cf20e458bc5a66710bd11780c
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
qdoc: attaching type of attached properties was missing

This bug was probably intoroduced when the QmlPropertyGroup
became a first class Node type. Otherwise, there is no way
to explain how it worked at all. But now qdoc includes the
attaching type.

Some debugging code was also cleaned up.

Task-number: QTBUG-35559
Change-Id: I478efb7f4356d51015af9f33c893958d4b4ae301
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
qdoc: Added 2nd argument to \generate list classes command

The qdoc command \generatelist has an argument that tells
qdoc which list to generate. When the argument is "classes"
qdoc generates the "All C++ Classes" list. qdoc looks for a
common prefix for all the members of the list and sorts the
members of the list using the character that follows the
common prefix. The problem was that the common prefix "Q"
was hardcoded in qdoc.

This update allows the \generate list command to have a
second argument, which is the common prefix. If the common
prefix is not provided, qdoc sorts the members of the list
on the first character.

There is only one use of the \generatelist command with
the classes argument in Qt5. It is changed to be
\generatelist classes Q, and the qdoc user manual is
updated to reflect this change.

Task-number: QTBUG-38226
Change-Id: Ie1011d728819a1e5598bbdf73b7444009377d231
Reviewed-by: Martin Smith <martin.smith@digia.com>