New function: install-r6rs!

* doc/ref/r6rs.texi (R6RS Incompatibilities): Document install-r6rs!.
* module/ice-9/boot-9.scm (install-r6rs!): New function.

doc/ref/r6rs.texi

@@ -106,6 +106,19 @@ Guile's implementation of @code{equal?} may fail to terminate when
 applied to arguments containing cycles.
 @end itemize
 
+Guile exposes a procedure in the root module to choose R6RS defaults
+over Guile's historical defaults.
+
+@deffn {Scheme Procedure} install-r6rs!
+Alter Guile's default settings to better conform to the R6RS.
+
+While Guile's defaults may evolve over time, the current changes that
+this procedure imposes are to add @code{.sls} and @code{.guile.sls} to
+the set of supported @code{%load-extensions}, to better support R6RS
+conventions.  @xref{Load Paths}.  Also, enable R6RS unicode escapes in
+strings; see the discussion above.
+@end deffn
+
 @node R6RS Standard Libraries
 @subsection R6RS Standard Libraries
 

module/ice-9/boot-9.scm

@@ -4069,6 +4069,19 @@ when none is available, reading FILE-NAME with READER."
 
 
 
+;;; {R6RS and R7RS}
+;;;
+
+(define (install-r6rs!)
+  "Make changes to the default environment to better conform to the
+R6RS.  @xref{R6RS Incompatibilities} in the manual."
+  (set! %load-extensions
+        (cons* ".guile.sls" ".sls"
+               (delete ".guile.sls" (delete ".sls" %load-extensions))))
+  (read-enable 'r6rs-hex-escapes))
+
+
+
 ;;; {Deprecated stuff}
 ;;;