When possible, use $(INSTALL).  This allows us to use the functionality within
install for setting directory / file permissions, a requirement for unprivileged
installation.

Also move any directory we plan to create within the installdirs macro. Plus
various other formatting issues.

(issue #17436)
Reported by: pabelanger
Patches:
      non-root.patch.v8 uploaded by pabelanger (license 224)
Tested by: pabelanger

Review: https://reviewboard.asterisk.org/r/654/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@278873 65c4cc65-6c06-0410-ace0-fbb531ad65f3