fix hyphen vs. minus in man pages

In troff '-' is used for a hyphen. A minus is denoted by '\-' . This is
normally also used for a dash.

This patch converts all '-'-s that are minuses or dashes to '\-'.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@256704 65c4cc65-6c06-0410-ace0-fbb531ad65f3