Add more hints for debugging make rules.

[Ralf Wildenhues]

Committing the doc update below to maint, for master and branch-1.11.

Also, I'm adding you to THANKS, Ludo and Andy, hoping that you'll be
providing more help in the near future anyway.  ;-)

Thanks,
Ralf

    Add more hints for debugging make rules.
    
    * doc/automake.texi (Debugging Make Rules): Show command to find
    out expanded values of variables; point to makefile debugger.
    * THANKS: Update.
    Prompted by suggestion from Ludovic Courtès and Andy Wingo.

diff --git a/doc/automake.texi b/doc/automake.texi
index 0fd233b..7484a76 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -11671,6 +11671,17 @@ Debugging Make Rules
 @code{make SHELL="/bin/bash -vx"} can help debug complex rules.
 @xref{The Make Macro SHELL,,, autoconf, The Autoconf Manual}, for some
 portability quirks associated with this construct.
address@hidden
address@hidden 'print: ; @@echo "$(VAR)"' | make -f Makefile -f - print}
+can be handy to examine the expanded value of variables.  You may need
+to use a target other than @samp{print} if that is already used or a
+file with that name exists.
address@hidden
address@hidden://bashdb.sourceforge.net/@/remake/} provides a modified
+GNU @command{make} command called @command{remake} that copes with
+complex GNU @command{make}-specific Makefiles and allows to trace
+execution, examine variables, and call rules interactively, much like
+a debugger.
 @end itemize