library: standardize portions of interface, <PIDS> api

This represents a rather major interface redesign. The
following highlights most of the changes/enhancements.

. The 'read' interface (employed by pgrep & pidof) saw
the biggest change. The 'open', 'next' and 'shut' guys
all went bye-bye, replaced by a single 'get' function.

. The items specified at 'new' time no longer serve as
the maximum. In fact, items & numitems are now treated
as optional, should callers prefer to wait until later
when the 'reset' function would then become mandatory.

. Even at 'reset' time, the stacks are not tied to any
sort of maximum. They will grow dynamically as needed.

. The order of some parameters was changed to parallel
that found in our other APIs. Specifically, when items
& numitems are needed they're specified in that order.

. A user will no longer be prevented from concurrently
employing any accessor functions. In other words, that
'get' (old 'read') won't preclude 'reap' and 'select'.

. A duplicate enumerator was found dealing with locked
resident pages. So, the name VM_LOCK was eliminated in
favor of VM_RSS_LOCKED, which is way more descriptive.

. The struct address returned to callers following any
reap() or select() is now more sharable as pids_fetch.

. Some input parameter names were changed to make them
more descriptive of the intended purpose/requirements.

------------------------------------------------------
Internally, there were numerous implementation changes
made that did not directly impact any potential users.

. That #define FPRINT_STACKS was eliminated along with
the associated supporting function and its invocation.

. Addresses returned following 'reap' or 'select' will
now be NULL delimited, so one has the option of stacks
access via the total count or this new NULL fencepost.

. Input params were simplified and generalized in both
oldproc_open() & close() to enable more than 1 PROCTAB
to be open simultaneously, which was required for get.

. The PROCPS_PIDS_logical_end enum was relocated after
the Item_table making the need to keep it synchronized
more apparent (if the table expands it's right there).

. The 'Public function' section of the source file was
subdivided into 1) the three basic required functions;
and 2) functions that can sometimes vary between APIs.

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

proc/libprocps.sym

@@ -25,15 +25,13 @@ global:
 	procps_ns_read_pid;
 	procps_pid_length;
 	procps_pids_new;
-	procps_pids_read_next;
-	procps_pids_read_open;
-	procps_pids_read_shut;
-	procps_pids_reap;
 	procps_pids_ref;
+	procps_pids_unref;
+	procps_pids_get;
+	procps_pids_reap;
 	procps_pids_reset;
 	procps_pids_select;
 	procps_pids_sort;
-	procps_pids_unref;
 	procps_slabinfo_new;
 	procps_slabinfo_read;
 	procps_slabinfo_ref;