qdoc's \include command now works as expected.
This command is only for including a file that
contains qdoc comments that contain qdoc commands
to be processed by qdoc. The file to be included
should have the .qdocinc suffix, although qdoc
will accept any suffix now. The file must be in
one of the directories specified by the sourcedirs
variable in the qdocconf file.

Task-number: QTBUG-33046
Change-Id: I45ea08932b4218aae369469968117fb5132f764b
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>