libcupsfilters, libppd, cups-browsed: 2.1.0 Releases including vulnerability fixes

Hi,

I have done 2.1.0 releases of libcupsfilters, libppd, and cups-browsed to 
include the recent security fixes done to prevent the Remote Code Execution 
(RCE) and DoS exploits reported.

See

https://openprinting.github.io/OpenPrinting-News-Flash-cups-browsed-Remote-Code-Execution-vulnerability/

Also included is libcups3 support for libcupsfilters and libppd (can now be 
built with either libcups2 or libcups3) and filter workflow testing (for build 
tests, CI, ...) in libcupsfilters.

And note that legacy CUPS browsing support and LDAP support are fully removed 
from cups-browsed now.

Here are the releases:

https://openprinting.github.io/libcupsfilters,-libppd,-cups-filters-2.1.0-Releases-including-vulnerability-fix/

There are also GitHub discussions set up for each release.

cups-filters 2.1.0 and 1.29.0 are not yet released as the fix of foomatic-rip is 
still in the works.

    Till