Patches #749830, #1144555: allow UNIX mmap size to default to current
file size.
diff --git a/Doc/lib/libmmap.tex b/Doc/lib/libmmap.tex
index d0fbf88..0d7baa1 100644
--- a/Doc/lib/libmmap.tex
+++ b/Doc/lib/libmmap.tex
@@ -62,8 +62,10 @@
                          prot\optional{, access}}}}
   \strong{(\UNIX{} version)} Maps \var{length} bytes from the file
   specified by the file descriptor \var{fileno}, and returns a mmap
-  object.
-
+  object.  If \var{length} is \code{0}, the maximum length of the map
+  will be the current size of the file when \function{mmap(} is
+  called.
+  
   \var{flags} specifies the nature of the mapping.
   \constant{MAP_PRIVATE} creates a private copy-on-write mapping, so
   changes to the contents of the mmap object will be private to this