library: ensure any 'flags' is consistently 'unsigned'

This commit is an outgrowth of the research into a bug
that recently surfaced with the 'w' program. And while
that program was just a victim several inconsistencies
were found in the handling of library flags during the
research. This patch just address such irregularities.

Reference(s):
http://www.freelists.org/post/procps/newlib-at-the-precipice,4

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

proc/readproc.c

@@ -1319,7 +1319,7 @@ end_procs:
 //////////////////////////////////////////////////////////////////////////////////
 
 // initiate a process table scan
-PROCTAB* openproc(int flags, ...) {
+PROCTAB* openproc(unsigned flags, ...) {
     va_list ap;
     struct stat sbuf;
     static int did_stat;
@@ -1401,7 +1401,7 @@ HIDDEN_ALIAS(readeither);
  * Free allocated memory with exit().  Access via tab[N]->member.  The pointer
  * list is NULL terminated.
  */
-proc_t** readproctab(int flags, ...) {
+proc_t** readproctab(unsigned flags, ...) {
     PROCTAB* PT = NULL;
     proc_t** tab = NULL;
     int n = 0;