a node name was changed in manual.texi which resulted in a very large
   ReadMe.txt file, as the generating script could not find the (renamed)
   ending node. Fixed the ending node name in Docs/Makefile.am and the 
   Docs/Support/generate-text-files.pl Perl script to make sure this does
   not happen again (I only discovered this because the Do-pkg script was
   not able to add the ReadMe.txt to the Apple Disk image because it ran out
   of disk space due to the size of the file)


Docs/Makefile.am:
   - Fixed a node name that was changed in manual.texi and resulted in
     the generation of a _very_ large ReadMe.txt file (down to the very end
     of the manual, since the ending node was not found)
Docs/Support/generate-text-files.pl:
   - added a safeguard: if the ending node was not found, abort with an error
     to indicate that the generated text file might be too large (as it would
     contain the whole manual, down from the starting node)
   - made some cosmetical changes