nipap/sql/Makefile: change order of execution and fix permission problem

functions.plsql depends on table created by ip_net.plsql so we should execute
this script first.

As postgres user there is a file system permission problem if I use the -f
option of psql to read the file. Using pipes fixed the problem.
nipap/sql/Makefile: create ip4r extension

This works only on postgres versions >= 9.1.
nipap/sql/Makefile: tell the user what exectly what to do
nipap/sql/Makefile: use pipe instead of -f option for psql
nipap/sql/Makefile: remove obsolete TODO about extension creation
Merge pull request #584 from booo/bug/nipap/sql/Makefile

fix nipap/sql/Makefile

The Makefile has drifted out of date and wasn't working properly...