(SLIB): Shorten the bit about core funcs overridden.

Don't want to duplicate the SLIB specs, and the set of modified bits
is likely to change over time and don't want to have to keep up with
that.

doc/ref/slib.texi

@@ -27,41 +27,11 @@ slib, The SLIB Manual}).  For example,
 @result{} #t
 @end example
 
-Note that the following Guile core functions are overridden by
-@code{(ice-9 slib)}, to implement SLIB specified semantics.
-
-@table @code
-@item delete-file
-@findex delete-file
-Returns @code{#t} for success or @code{#f} for failure
-(@pxref{Input/Output,,, slib, The SLIB Manual}), as opposed to the
-Guile core version unspecified for success and throwing an error for
-failure (@pxref{File System}).
-
-@c  `provide' is also exported by ice-9 slib, but its definition in
-@c  slib require.scm is the same as guile boot-9.scm, so believe
-@c  nothing needs to be said about that.
-
-@item provided?
-@findex provided?
-Accepts a feature specification containing @code{and} and @code{or}
-forms combining symbols (@pxref{Feature,,, slib, The SLIB Manual}), as
-opposed to the Guile core taking only plain symbols (@pxref{Feature
-Manipulation}).
-
-@item open-file
-@findex open-file
-Takes a symbol @code{r}, @code{rb}, @code{w} or @code{wb} for the open
-mode (@pxref{Input/Output,,, slib, The SLIB Manual}), as opposed to
-the Guile core version taking a string (@pxref{File Ports}).
-
-@item system
-@findex system
-Returns a plain exit code 0 to 255 (@pxref{System Interface,,, slib,
-The SLIB Manual}), as opposed to the Guile core version returning a
-wait status that must be examined with @code{status:exit-val} etc
-(@pxref{Processes}).
-@end table
+A few Guile core functions are overridden by the SLIB setups; for
+example the SLIB version of @code{delete-file} returns a boolean
+indicating success or failure, whereas the Guile core version throws
+an error for failure.  In general (and as might be expected) when SLIB
+is loaded it's the SLIB specifications which are followed.
 
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