Add note about pkg.conf not being needed at all.

Clean up some of the alias examples:

    pkg info -i -g -x foo   -> pkg info -ix foo
    pkg search -i -g -x foo -> pkg search -ix foo

      Non-sensical combination of globbing and regex search.
      Arbitrarily choose regex.  Also '-i' is the default now, but
      keep it in these command lines so the work irrespective of the
      setting of CASE_SENSITIVE_MATCH

   pkg info -Cx foo
   pkg search -Cx foo

      Add the 'orced to case sensitive' equivalents.

Reported by az|_ via IRC.
First cut at reworking alias expansion so that it copes with quoted
strings in the alias arglists.  It's not exactly the same as the way
the shell breaks a command line into arguments, but similar.

This standard example now works:

ALIAS              : {
  ...
  leaf: query -e "%a == 0" "%n-%v",
  ...
}

by replacing the argv[0]:

leaf

inserting the following as argv[0] .. argv[3] and shifting any
remaining args down:

query
-e
%a == 0
%n-%v

A quoted argument extends to the next matching quote mark, or the end
of the alias string.  There's no check for balanced quote marks, nor
is any error message issued if quotes are not closed.  There's no
provision for escaping quote marks like so: \" (despite what pkg -vv
outputs).

You can use "double" or 'single' quotes interchangeably; the only
difference is that within a pair of "double quotes" a sigle quote "'"
loses it's special meaning and is copied verbatim into the expanded
argv.  And vice-versa for a double quote in a single-quoted argument.
Merge branch 'master' of github.com:freebsd/pkg