library: rework namespace calls

Functions related to namespaces were half-in half-out of the
procps library and didn't fit the standard naming scheme.

While struct { long ns[x]} is a bit clunky, its the only way
to "lock in" x. The alternative is to use ns_* variables.

This work was needed before pgrep could be converted.

include/Makefile.am

@@ -2,7 +2,6 @@ dist_noinst_HEADERS = \
 	c.h \
 	fileutils.h \
 	nls.h \
-	nsutils.h \
 	rpmatch.h \
 	signals.h \
 	strutils.h \

include/nsutils.h

@@ -1,7 +0,0 @@
-#ifndef PROCPS_NG_NSUTILS
-#define PROCPS_NG_NSUTILS
-
-#include "proc/readproc.h"
-int ns_read(pid_t pid, proc_t *ns_task);
-
-#endif