I noticed that Doxygen was also complaining about the "<asis>" and "<bs>"
tags. So convert those to the backslash form like we did for "<outp>" in the
previous commit.
Doxygen has been warning that `<outp>` and `</outp>` are not valid XML/HTML commands since commit cb6d5d76 on 20016-04-04. That's primarily because there is at present no way to tell Doxygen to recognize new XML/HTML tags. The actual errors look like this:
```
.../string.doxygen:187: warning: Unsupported xml/html tag </outp> found
```
I hate build errors since they a) cause needless concern, and b) make it harder to notice when I've introduced a new error. So switch from XML/C## style markup to Doxygen style markup for the "outp" annotation.
Completely fixes#1557 and the underlying Doxygen changes that caused
it. Should make fish docs simpler and more robust, more consistent and
generally prettier.
todo:
- trap unmarked text as arguments in context
- test & fix sed portability - see in particular. (so far tested on BSD
(Mac) and GNU sed).
- test Makefile changes
- last round of aesthetic changes and getting that ascii fish in there…
Rework for Doxygen >1.8. Moved large parts of the documentation to a
simplified format, making use of Markdown enhancements and fixing bad
long options.
