Doc: further fooling-about with rendering of tables in PDF output.

I concluded that we really just ought to force all tables in PDF output
to default to "left" alignment (instead of "justify"); that is what the
HTML toolchain does and that's what most people have been designing the
tables to look good with.  There are few if any places where "justify"
produces better-looking output, and there are many where it looks
horrible.  So change stylesheet-fo.xsl to make that true.

Also tweak column widths in a few more tables to make them look better
and avoid "exceed the available area" warnings.  This commit fixes
basically everything that can be fixed through that approach.  The
remaining tables that give warnings either are scheduled for redesign
as per recent discussions, or need a fundamental rethink because they
Just Don't Work in a narrow view.

doc/src/sgml/json.sgml

@@ -132,6 +132,9 @@
   <table id="json-type-mapping-table">
      <title>JSON Primitive Types and Corresponding <productname>PostgreSQL</productname> Types</title>
      <tgroup cols="3">
+      <colspec colname="col1" colwidth="1*"/>
+      <colspec colname="col2" colwidth="1*"/>
+      <colspec colname="col3" colwidth="2*"/>
       <thead>
        <row>
         <entry>JSON primitive type</entry>
@@ -742,6 +745,8 @@ SELECT jdoc-&gt;'guid', jdoc-&gt;'name' FROM api WHERE jdoc @&gt; '{"tags": ["qu
   <table id="type-jsonpath-variables">
    <title><type>jsonpath</type> Variables</title>
    <tgroup cols="2">
+    <colspec colname="col1" colwidth="1*"/>
+    <colspec colname="col2" colwidth="2*"/>
     <thead>
      <row>
       <entry>Variable</entry>
@@ -777,6 +782,8 @@ SELECT jdoc-&gt;'guid', jdoc-&gt;'name' FROM api WHERE jdoc @&gt; '{"tags": ["qu
   <table id="type-jsonpath-accessors">
    <title><type>jsonpath</type> Accessors</title>
    <tgroup cols="2">
+    <colspec colname="col1" colwidth="1*"/>
+    <colspec colname="col2" colwidth="2*"/>
     <thead>
      <row>
       <entry>Accessor Operator</entry>