Fix cols of reserved keywords table

The table of reserved keywords obviously has four columns, and this
should be reflected by the `col` attribute (although that is apparently
ignored by PhD for now).  We also specify four columns for the table of
soft reserved words.

Author: cmb69

appendices/reserved.xml

@@ -512,7 +512,7 @@
    <para>
     <table>
      <title>Reserved words</title>
-     <tgroup cols="5">
+     <tgroup cols="4">
       <tbody>
        <row>
         <entry>
@@ -569,7 +569,7 @@
    <para>
     <table>
      <title>Soft reserved words</title>
-     <tgroup cols="5">
+     <tgroup cols="4">
       <tbody>
        <row>
         <entry>