Modernize postgres support

`depends_on :postgresql` will handle non-Homebrew postgres for us.
Detect branch and extension names from nested constants
Call super without parens
Move option into relevant formula
Return strings from php_version and php_version_path
Pathname#+ appends the path separator
Don't pass nonexistent options to the php configure script
Manipulating PKG_CONFIG_LIBDIR is not necessary
Set PHP_AUTOCONF and PHP_AUTOHEADER via ENV
Use ruby
Use opt helpers
Update phpmyadmin to version 4.3.4
Update php5x-redis to 2.2.6
php53-redis: add 2.2.6 bottle.
php54-redis: add 2.2.6 bottle.
php55-redis: add 2.2.6 bottle.
php56-redis: add 2.2.6 bottle.