classify: add pcap/trace classfier mgmt API calls

Add lookup/get/set API calls to manage both PCAP and Trace
filtering Classifier tables.

The "lookup" call may be used to identify a Classifier table
within a chain of tables taht matches a particular mask vector.
For efficiency, this call should be used to determine to which
table a match vector should be added.

The "get" calls return the first table within a chain (either
a PCAP or the Trace) set of tables.  The "set" call may be
used to add a new table to one such chain.  If the "sort_masks"
flag is set, the tables within the chain are ordered such that
the most-specific mask is first, and the least-specific mask
is last.  A call that "sets" a chain to ~0 will delete and free
all the tables with a chain.

The PCAP filters are per-interface, with "local0", (that is,
sw_if_index == 0) holding the system-wide PCAP filter.

The Classifier used a reference-counted "set" for each PCAP
or trace filter that it stored.  The ref counts were not used,
and the vector of tables was only used temporarily to establish
a sorted order for tables based on masks.  None of that
complexity was actually warranted, and where it was used,
the same could be achieved more simply.

Type: refactor

Signed-off-by: Jon Loeliger <jdl@netgate.com>
Change-Id: Icc56116cca91b91c631ca0628e814fb53f3677d2
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 766c9ec..adfdc87 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -77,8 +77,7 @@
 typedef struct
 {
   u8 trace_filter_enable;
-  u32 trace_classify_table_index;
-  u32 trace_filter_set_index;
+  u32 classify_table_index;
 } vlib_trace_filter_t;
 
 typedef enum