* activated via bit 4 of the ED flag (enabled by default)
 * automatic EOL guessing on file loading and translation to LFs.
   * works with files that have inconsistent EOL sequences.
 * automatic translation to original EOL sequences on file saving
   * works with inconsistent EOL sequences in the buffer.
     This should usually not happen if the file was read in with
     automatic EOL translation enabled.
 * also works with the EC and EG commands
 * performance is OK, depending on the file being translated.
   When reading files with UNIX EOLs, the overhead is minimal
   typically-sized files. For DOS EOLs the overhead is larger
   but still acceptable.
 * Return (line feed) is now an immediate editing command.
   This centralizes EOL sequence insertion.
   Later, other features like auto-indent could be added to
   the editing command.
 * get_eol() has been moved to main.cpp (now called
   get_eol_seq()
 * Warn if file ownership could not be preserved when
   saving files.
 * IOView has been almost completely rewritten based
   on GIOChannels. The EOL translation code is also in IOView.

 * acts as a safe-guard against uninterrupted infinite loops
   or other operations that are costly to undo in interactive mode.
   If we're out of memory, it is usually too late to react properly.
   This implementation tries to avoid OOMs due to SciTECO behaviour.
   We cannot fully exclude the chance of an OOM error.
 * The undo stack size is only approximated using the
   UndoToken::get_size() method.
   Other ways to measure the exact amount of allocated heap
   (including size fields in every heap object or using sbrk(0) and
   similar) are either costly in terms of memory or platform-specific.
   This implementation does not need any additional memory per heap
   object or undo token but exploits the fact that undo tokens
   are virtual already. The size of an undo token is determined
   at compile time.
 * Default memory limit of 500mb should be OK for most people.
 * The current limit can be queried with "2EJ" and set with <x>,2EJ.
   This also works interactively (a bit tricky!)
 * Limiting can be disabled. In this case, undo token processing
   is a bit faster.
 * closes #3

 * also did some whitespace cleanup in SciTECO now that tabs are
   displayed properly