Making pg_hba.conf case-insensitive

I was looking at this TODO item from 2009:

    https://www.postgresql.org/message-id/4AA7B197.70002%40usit.uio.no

I have implemented this in the attached patch.  It does two things:

o  compares words in columns that can only support keywords as
case-insensitive, double-quoted or not

o  compares words in columns that can contain user/db names or keywords
as case-sensitive if double-quoted, case-insensitive if not

Here is the 'local' line we install during initdb, and a newly
identically-behaving line:

    # TYPE  DATABASE        USER            ADDRESS                 METHOD
    local   all             all                                     trust
    "LOCAL" ALL             ALL                                     TRUST

This 9.6 line:

    local   Test            all                                     trust

would have to be represented in PG 10 as:

    local   "Test"          all                                     trust

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I. As I am, so you will be. +
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