ppp: Update to version 2.5.2

ppp: Update to version 2.5.2

- Update from version 2.5.1 to 2.5.2
- Update of rootfile
- Changelog
    2.5.2
	Some old and probably unused code has been removed, notably the pppgetpass program and the passprompt plugin, and some of the files in the sample and
	 scripts directories.
	If a remote number has been set, it is available to scripts in the REMOTENUMBER
	 environment variable.
	The Solaris port has been updated, including updated installation instructions
	 in README.sol2.
	Various other bug fixes and minor enhancements.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>