dox: Reorganize the file & add Simdize group
dox: Reorganize the file & add Simdize group

* Remove most of the asterisks and tell vim that the filetype is
doxygen, for nicer syntax highlighting.
* Reorganize the group definitions into \defgroup (for defining the
order) and \addtogroup (for defining the contents).

Signed-off-by: Matthias Kretz <372ea4eca737a13cd010ee806d4ce7b98ee71550@kde.org>

chr-engwer/Vc,VcDevel/Vc,chr-engwer/Vc,VcDevel/Vc,VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc