Fix for special characters in Doxygen comments.

Escape "-" characters in the beginning of the paragraph as they are not
handled properly by Doxygen otherwise.

Escape the space after "i.e." to prevent the brief doc string from being
terminated by it.

Escape "--" which is translated to a dash by Doxygen otherwise.

Closes #15228.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74064 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775