doc: Do not gender the programmer.

* doc/ref/api-foreign.texi: Replace "his" with "their".
* doc/ref/sxml.texi: Likewise.

doc/ref/api-foreign.texi

@@ -52,7 +52,7 @@ automatically the next time they are run.
 
 Now, when all the necessary machinery is there to perform part of the
 linking at run-time, why not take the next step and allow the programmer
-to explicitly take advantage of it from within his program?  Of course,
+to explicitly take advantage of it from within their program?  Of course,
 many operating systems that support shared libraries do just that, and
 chances are that Guile will allow you to access this feature from within
 your Scheme programs.  As you might have guessed already, this feature

doc/ref/sxml.texi

@@ -275,7 +275,7 @@ the middle- and high-level parsers are single-threaded through the
 the @var{seed} in any way: they simply pass it around as an instance of
 an opaque datatype.  User functions, on the other hand, can use the seed
 to maintain user's state, to accumulate parsing results, etc.  A user
-can freely mix his own functions with those of the framework.  On the
+can freely mix their own functions with those of the framework.  On the
 other hand, the user may wish to instantiate a high-level parser:
 @code{SSAX:make-elem-parser} or @code{SSAX:make-parser}.  In the latter
 case, the user must provide functions of specific signatures, which are