Re: [PATCH] Add pretty-printed XML output option

As suggested by Peter and Nikolay, v15 now removes the xmlformat
function from the catalog and adds the [NO] INDENT option to
xmlserialize, as described in X069.\

gitpod=# select xmlserialize(document '<xml><more>13</more></xml>' as text indent);
              xmlserialize              
----------------------------------------
 <?xml version="1.0" encoding="UTF-8"?>+
 <xml>                                 +
   <more>13</more>                     +
 </xml>                                +
 
(1 row)

gitpod=# select xmlserialize(document '<xml>text<more>13</more></xml>' as text indent);
              xmlserialize              
----------------------------------------
 <?xml version="1.0" encoding="UTF-8"?>+
 <xml>text<more>13</more></xml>        +