doc: Fix typos in the manual.

* doc/ref/api-control.texi:
* doc/ref/r6rs.texi:
* doc/ref/sxml.texi: Fix typos.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

doc/ref/api-control.texi

@@ -678,8 +678,8 @@ Evaluate @var{expr} in a prompt, optionally specifying a tag and a
 handler.  If no tag is given, the default prompt tag is used.
 
 If no handler is given, a default handler is installed.  The default
-handler accepts a procedure of one argument, which will called on the
-captured continuation, within a prompt.
+handler accepts a procedure of one argument, which will be called on
+the captured continuation, within a prompt.
 
 Sometimes it's easier just to show code, as in this case:
 

doc/ref/r6rs.texi

@@ -1173,7 +1173,7 @@ evaluates to @code{baz}.
 
 @deffn {Scheme Procedure} raise obj
 Equivalent to core Guile @code{(raise-exception @var{obj})}.
-@xref{Raising and Handling Exceptions}.  p(Unfortunately, @code{raise}
+@xref{Raising and Handling Exceptions}.  (Unfortunately, @code{raise}
 is already bound to a different function in core Guile.
 @xref{Signals}.)
 @end deffn

doc/ref/sxml.texi

@@ -230,7 +230,7 @@ SAX parsers were created to give the programmer more control on the
 parsing process.  A programmer gives the SAX parser a number of
 ``callbacks'': functions that will be called on various features of the
 XML stream as they are encountered.  SAX parsers are more efficient, but
-much harder to user, as users typically have to manually maintain a
+much harder to use, as users typically have to manually maintain a
 stack of open elements.
 
 Kiselyov realized that the SAX programming model could be made much