[Vim-l] Cpp is now C++

[John Beckett]

One small step...

Page titles are now allowed to contain '+'.

I have completed:
- Renamed all tips with 'Cpp' in title to 'C++'.
- Changed corresponding VimTip redirect pages.
- Duplicated old category 'C plus plus' to new category:C++.
- Flagged old category 'C plus plus' for deletion.
- Reworded Title guidelines to indicate can use 'C++'.

I would still avoid using "C++" in a title (is the tip really about C++?). However,
where it makes sense, a tip title can certainly use "C++".

The category is now [[Category:C++]].

Note that 'C#' will never be valid in a title, so it's 'C sharp' and [[Category:C
sharp]].

John