tcp: better congestion control defaults

[imp]

Summary

Define CC_NEWRENO in all the appropriate DEFAULTS and std.* config
files. It's the default congestion control algorithm. Add code to cc.c
so that CC_DEFAULT is "newreno" if it's not overriden in the config
file.

Sponsored by: Netflix

[• hselasky]

Looks good.

[andrew]

It might pay to switch to options<space><tab>CC_NEWRENO while here to make its style consistent with the other options.

[jhb]

+1 to using the normal style (options<space><tab>)

[manu]

Thanks, looks saner that way.
Same comment than Andrew and John though :)