Trying to address Robert Kerns review comments.

* ~ not ^

* = skipped for -

* swap - and = underline in files they are swapped

* * to = in header underline

* - to = and * to - for consitency

* A few more change * -> ~

* use ~ instead of +

* DOC: Fixup `c-api/array.rst` with further ^ with ~ replacement

There is still a fourth level here, which remains using "

Co-authored-by: Sebastian Berg <sebastian@sipsolutions.net>

Based on
https://mail.python.org/pipermail/numpy-discussion/2020-December/081323.html