top: adapt for running with proc mounted as subset=pid

As the issue cited below illustrates, a pids namespace
with proc mounted as subset=pid denies our library any
access to non-task data. In top's case, the result was
a fatal error message which involved "cpu statistics".

With this patch top will now assume an error involving
global cpu (stat) or memory (meminfo) data means we're
running under a restricted pids namespace. As such, an
attempt will be made to still display task level data.

[ if our assumption is incorrect, it's of no matter. ]
[ instead of a fatal error, we'll still try to offer ]
[ a user some minimally useful bit of functionality. ]

Reference(s):
https://gitlab.com/procps-ng/procps/-/issues/227
https://www.freelists.org/post/procps/three-for-newlib,1
. 1st cut at subset=pid
commit bcb837b8c7

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

top/top_nls.h

@@ -84,7 +84,7 @@ enum norm_nls {
    WORD_process_txt, WORD_threads_txt, WRITE_rcfile_fmt, WRONG_switch_fmt,
    XTRA_badflds_fmt, XTRA_fixwide_fmt, XTRA_modebad_txt, XTRA_size2up_txt,
    XTRA_vforest_fmt, XTRA_warncfg_txt, XTRA_warnold_txt, XTRA_winsize_txt,
-   X_SEMAPHORES_fmt, X_THREADINGS_fmt,
+   X_RESTRICTED_txt, X_SEMAPHORES_fmt, X_THREADINGS_fmt,
 #ifndef INSP_OFFDEMO
    YINSP_demo01_txt, YINSP_demo02_txt, YINSP_demo03_txt, YINSP_deqfmt_txt,
    YINSP_deqtyp_txt, YINSP_dstory_txt,