library: eliminated the questionable 'procps.h' header

There was a time when that procps.h file served a more
traditional role. Prior to the commit referenced below
it held just macros plus manifest constants. But, with
that change, such items were replaced with a series of
includes embracing all the library exported functions.

That approach was known to disguise errors which would
have otherwise yielded a compiler warning. And without
such a warning, there was no way to address the error.

So this patch will trade the all inclusive header file
approach for individual includes only where necessary.

Reference(s):
. April 2016, procps.h header file revamped
commit ccb6ae8de1
. Sept 2018, top abandoned use of procps.h
commit a6dfc2382e

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

proc/readproc.c

@@ -19,12 +19,6 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
-#include "version.h"
-#include "readproc.h"
-#include "escape.h"
-#include "pwcache.h"
-#include "devname.h"
-#include "procps.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
@@ -41,7 +35,13 @@
 #ifdef WITH_SYSTEMD
 #include <systemd/sd-login.h>
 #endif
-#include <proc/namespace.h>
+
+#include "devname.h"
+#include "escape.h"
+#include "namespace.h"
+#include "pwcache.h"
+#include "readproc.h"
+#include "version.h"
 
 // sometimes it's easier to do this manually, w/o gcc helping
 #ifdef PROF