This is part of the multithreading journey. The parser and lexer were
using loads of global variables and all of these are now packed into
struct cf_context and others.
Note that the config API has changed:
* cfg_alloc[zu]?(size) is now cf_alloc[zu]?(ctx, size)
* cf_error(msg, ...) is now cf_error(ctx, msg, ...)
* config_parse() and cli_parse() are now called differently
* there is a brand new CF_CTX section in *.Y files which participates
in struct cf_context construction
The patch implements Default Router Preferences and More-Specific Routes
(RFC 4191) for RAdv protocol, allowing to announce router preference and
more specific routes in router advertisements. Routes can be exported to
RAdv like to regular routing protocols.
Some cleanups, bugfixes and other changes done by Ondrej Zajicek.
The patch adds support for channels, structures connecting protocols and
tables and handling most interactions between them. The documentation is
missing yet.
The RAdv protocol could be configured to change its behavior based on
availability of routes, e.g., do not announce router lifetime when a
default route is not available.
