[docs] [tools] Fix see also links

Summary: Changes "see also" links to use :manpage: instead of plain text or the form `name|name` which was being treated literally, not as a link.

Reviewers: jhenderson, rupprecht

Reviewed By: jhenderson

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63970

llvm-svn: 365159