Fix ill-advised placement of PGRES_COPY_BOTH enum value.

It must be added at the end of the ExecStatusType enum to avoid ABI
breakage compared to previous libpq versions.  Noted by Magnus.

Author: tglsfdc

doc/src/sgml/libpq.sgml

@@ -2196,16 +2196,6 @@ ExecStatusType PQresultStatus(const PGresult *res);
           </listitem>
          </varlistentry>
 
-         <varlistentry id="libpq-pgres-copy-both">
-          <term><literal>PGRES_COPY_BOTH</literal></term>
-          <listitem>
-           <para>
-            Copy In/Out (to and from server) data transfer started.  This is
-            currently used only for streaming replication.
-           </para>
-          </listitem>
-         </varlistentry>
-
          <varlistentry id="libpq-pgres-bad-response">
           <term><literal>PGRES_BAD_RESPONSE</literal></term>
           <listitem>
@@ -2232,6 +2222,16 @@ ExecStatusType PQresultStatus(const PGresult *res);
            </para>
           </listitem>
          </varlistentry>
+
+         <varlistentry id="libpq-pgres-copy-both">
+          <term><literal>PGRES_COPY_BOTH</literal></term>
+          <listitem>
+           <para>
+            Copy In/Out (to and from server) data transfer started.  This is
+            currently used only for streaming replication.
+           </para>
+          </listitem>
+         </varlistentry>
         </variablelist>
 
         If the result status is <literal>PGRES_TUPLES_OK</literal>, then

src/interfaces/libpq/fe-exec.c

@@ -35,10 +35,10 @@ char	   *const pgresStatus[] = {
 	"PGRES_TUPLES_OK",
 	"PGRES_COPY_OUT",
 	"PGRES_COPY_IN",
-	"PGRES_COPY_BOTH",
 	"PGRES_BAD_RESPONSE",
 	"PGRES_NONFATAL_ERROR",
-	"PGRES_FATAL_ERROR"
+	"PGRES_FATAL_ERROR",
+	"PGRES_COPY_BOTH"
 };
 
 /*

src/interfaces/libpq/libpq-fe.h

@@ -85,11 +85,11 @@ typedef enum
 								 * contains the result tuples */
 	PGRES_COPY_OUT,				/* Copy Out data transfer in progress */
 	PGRES_COPY_IN,				/* Copy In data transfer in progress */
-	PGRES_COPY_BOTH,			/* Copy In/Out data transfer in progress */
 	PGRES_BAD_RESPONSE,			/* an unexpected response was recv'd from the
 								 * backend */
 	PGRES_NONFATAL_ERROR,		/* notice or warning message */
-	PGRES_FATAL_ERROR			/* query failed */
+	PGRES_FATAL_ERROR,			/* query failed */
+	PGRES_COPY_BOTH				/* Copy In/Out data transfer in progress */
 } ExecStatusType;
 
 typedef enum