library: play catchup with a new proc_t 'cgname' field

library: play catchup with a new proc_t 'cgname' field

Since we're about to break the ABI/API anyway, why not
go ahead and add yet another field to our proc_t which
the newlib branch has had for awhile. This then allows
the top program to offer 'control group name' and will
also permit a few reductions in that ps program logic.

And let's also clean up some unrelated warnings below.

Clang warnings:
proc/readproc.c:1178:50: warning: address of array 'ent->d_name' will always evaluate to 'true' [-Wpointer-bool-conversion]
    if(unlikely(unlikely(!ent) || unlikely(!ent->d_name))) return 0;
                                           ~~~~~~^~~~~~
proc/readproc.c:1205:50: warning: address of array 'ent->d_name' will always evaluate to 'true' [-Wpointer-bool-conversion]
    if(unlikely(unlikely(!ent) || unlikely(!ent->d_name))) return 0;
                                           ~~~~~~^~~~~~

Signed-off-by: Jim Warner <james.warner@comcast.net>