In docs, rename "backwards compatibility" to "backward compatibility"

for consistency.

doc/src/sgml/array.sgml

@@ -646,7 +646,7 @@ SELECT f1[1][-2][3] AS e1, f1[1][-1][5] AS e2
    If the value written for an element is <literal>NULL</> (in any case
    variant), the element is taken to be NULL.  The presence of any quotes
    or backslashes disables this and allows the literal string value
-   <quote>NULL</> to be entered.  Also, for backwards compatibility with
+   <quote>NULL</> to be entered.  Also, for backward compatibility with
    pre-8.2 versions of <productname>PostgreSQL</>, the <xref
    linkend="guc-array-nulls"> configuration parameter can be turned
    <literal>off</> to suppress recognition of <literal>NULL</> as a NULL.

doc/src/sgml/config.sgml

@@ -5357,7 +5357,7 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
         null values to be entered.  However, <productname>PostgreSQL</> versions
         before 8.2 did not support null values in arrays, and therefore would
         treat <literal>NULL</> as specifying a normal array element with
-        the string value <quote>NULL</>.  For backwards compatibility with
+        the string value <quote>NULL</>.  For backward compatibility with
         applications that require the old behavior, this variable can be
         turned <literal>off</>.
        </para>

doc/src/sgml/func.sgml

@@ -9695,7 +9695,7 @@ nextval('foo')              <lineannotation>searches search path for <literal>fo
     Before <productname>PostgreSQL</productname> 8.1, the arguments of the
     sequence functions were of type <type>text</>, not <type>regclass</>, and
     the above-described conversion from a text string to an OID value would
-    happen at run time during each call.  For backwards compatibility, this
+    happen at run time during each call.  For backward compatibility, this
     facility still exists, but internally it is now handled as an implicit
     coercion from <type>text</> to <type>regclass</> before the function is
     invoked.

doc/src/sgml/libpq.sgml

@@ -1313,7 +1313,7 @@ char *PQport(const PGconn *conn);
        Returns the debug <acronym>TTY</acronym> of the connection.
        (This is obsolete, since the server no longer pays attention
        to the <acronym>TTY</acronym> setting, but the function remains
-       for backwards compatibility.)
+       for backward compatibility.)
 
 <synopsis>
 char *PQtty(const PGconn *conn);
@@ -6933,7 +6933,7 @@ ldap://ldap.acme.com/cn=dbserver,cn=hosts?pgconnectinfo?base?(objectclass=*)
    The default value for <literal>sslmode</> is <literal>prefer</>. As is shown
    in the table, this makes no sense from a security point of view, and it only
    promises performance overhead if possible. It is only provided as the default
-   for backwards compatibility, and is not recommended in secure deployments.
+   for backward compatibility, and is not recommended in secure deployments.
   </para>
 
  </sect2>

doc/src/sgml/lobj.sgml

@@ -114,7 +114,7 @@ Oid lo_creat(PGconn *conn, int mode);
 
      <replaceable class="parameter">mode</replaceable> is unused and
      ignored as of <productname>PostgreSQL</productname> 8.1; however, for
-     backwards compatibility with earlier releases it is best to
+     backward compatibility with earlier releases it is best to
      set it to <symbol>INV_READ</symbol>, <symbol>INV_WRITE</symbol>,
      or <symbol>INV_READ</symbol> <literal>|</> <symbol>INV_WRITE</symbol>.
      (These symbolic constants are defined

doc/src/sgml/plperl.sgml

@@ -202,7 +202,7 @@ select returns_array();
   <para>
    Perl passes <productname>PostgreSQL</productname> arrays as a blessed
    PostgreSQL::InServer::ARRAY object. This object may be treated as an array
-   reference or a string, allowing for backwards compatibility with Perl
+   reference or a string, allowing for backward compatibility with Perl
    code written for <productname>PostgreSQL</productname> versions below 9.1 to
    run.  For example:
 

doc/src/sgml/user-manag.sgml

@@ -384,7 +384,7 @@ RESET ROLE;
     roles being used as SQL roles the <literal>INHERIT</> attribute, while
     giving roles being used as SQL users the <literal>NOINHERIT</> attribute.
     However, <productname>PostgreSQL</productname> defaults to giving all roles
-    the <literal>INHERIT</> attribute, for backwards compatibility with pre-8.1
+    the <literal>INHERIT</> attribute, for backward compatibility with pre-8.1
     releases in which users always had use of permissions granted to groups
     they were members of.
    </para>

doc/src/sgml/xfunc.sgml

@@ -1368,7 +1368,7 @@ CREATE FUNCTION test(int, int) RETURNS int
     The <quote>body</quote> of the function definition
     specifies the C-language name of the function, which need not be the
     same as the name being declared for SQL use.
-    (For reasons of backwards compatibility, an empty body
+    (For reasons of backward compatibility, an empty body
     is accepted as meaning that the C-language function name is the
     same as the SQL name.)
    </para>
@@ -2701,7 +2701,7 @@ typedef struct
     /*
      * OPTIONAL pointer to result slot
      *
-     * This is obsolete and only present for backwards compatibility, viz,
+     * This is obsolete and only present for backward compatibility, viz,
      * user-defined SRFs that use the deprecated TupleDescGetSlot().
      */
     TupleTableSlot *slot;