Document ms FR string more.

* NEWS: Add news item.
* doc/groff.texi (ms Document Control Settings): Clarify when changes to
  FR take effect.  Add motivation for new string and its default value.
  Advise users to migrate from \n[FL] (now otherwise undocumented) to
  \*[FR].  Explain how to simulate old absolute setting effect of \n[FL]
  for those whose recall of *roff arithmetic and/or the zero product
  property is poor.  Supply example.
* doc/ms.ms (Document control settings): Sync with the above.
* tmac/groff_ms (Usage/Document control registers): Drop documentation
  of FL register.  Clarify when changes to FR take effect.

1 files changed, 18 insertions, 4 deletions

diff --git a/NEWS b/NEWS
index 69ceb6e0f..017e4508c 100644
--- a/NEWS
+++ b/NEWS
@@ -118,10 +118,24 @@ o The doc (mdoc) macro package now honors the HY register as the an
   furthermore recognizes but ignores the AD string (see above) for
   compatibility with an (man).
 
-o The s (ms) macro package has changed the default footnote line length
-  (\n[FL]) from 5/6ths of the text line length (\n[LL]) to 11/12ths for
-  better compatibility with ms documents prepared with AT&T ms or its
-  descendant implementations in Heirloom Doctools and neatroff.
+o The s (ms) macro package supports a new string, FR, which defines the
+  ratio of the footnote line length to the current line length.
+  The default expression is "11/12", 11/12ths of the normal line length,
+  adopted for better compatibility with ms documents prepared with AT&T
+  ms or its descendant implementations in Heirloom Doctools and
+  neatroff.  This is a change from previous groff releases, which used a
+  ratio of 5/6ths.
+
+  You may wish to set the FR string to 1 to align with contemporary
+  typesetting practices.  In Version 7 Unix ms, its descendants, and
+  groff prior to this release, an FL register was used for the line
+  length in footnotes; however, setting this register at document
+  initialization time had no effect on the footnote line length in
+  multi-column arrangements.
+
+  FR should be used in preference to the old FL register in contemporary
+  documents.  See the groff Texinfo manual or the "Using groff with the
+  ms macros" document, also part of this release, for more information.
 
 o The s (ms) macro package has added strings, \*< and \*>, to perform
   subscripting within a paragraph.  They work analogously to the \*{ and