m4: Update to version 1.4.20

m4: Update to version 1.4.20

- Update from version 1.4.19 to 1.4.20
- Update of rootfile
- Changelog
    1.4.20
	** Fix a bug in the `eval' builtin where it does not suppress warnings
	   about division by zero that occurs within a more complex expression on
	   the right hand side of || or && (present since short-circuiting was
	   introduced in 1.4.8b).
	** The `syscmd' and `esyscmd' builtins no longer mishandle a command line
	   starting with `-' or `+' (present since "the beginning").
	** Fix regression introduced in 1.4.19 where trace output (such as with
	   `debugmode(t)') could read invalid memory when tracing a series of
	   pushed macros that are popped during argument collection.
	** Fix regression introduced in 1.4.19 where the `format' builtin
	   inadvertently took on locale-dependent parsing and output of floating
	   point numbers as a side-effect of introducing message translations.
	   While it would be nice for m4 to be fully locale-aware, such a behavior
	   change belongs in a major version release such as 1.6, and not a minor
	   release.
	** Fix regression introduced in 1.4.11 where the experimental `changeword'
	   builtin could cause a crash if given a regex that does not match all
	   one-byte prefixes of valid longer matches.  As a reminder, `changeword'
	   is not recommended for production use, and will likely not be present
	   in the next major version release.
	** On non-Unix platforms where binary files differ from text, loading a
	   frozen file (which should be cross-platform compatible) now correctly
	   uses binary mode.
	** Several documentation improvements to the manual.
	** Update to comply with newer C standards, and inherit portability
	   improvements from gnulib.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>