start putting the URI parsing code in one place,

start putting the URI parsing code in one place,
introducing the function parse_uri() that splits
a URI in its components.

Right now use it only in one place, because the custom
parsing that is done here and there sometimes has
bugs that i want to figure out first.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@45965 65c4cc65-6c06-0410-ace0-fbb531ad65f3