Make query classifier self-contained.

Only the query classifier needs the functionality of the embedded
server, while the rest of MaxScale is content with the client
library or Connector/C.

This have now been rearranged so that query-classifier links with
the embedded static library and then explicitly exports its own
functions using the query_classifier.map linker script. That way
query classifier will use the embedded library, while the rest of
maxscale use the client library, and this without conflicts.

Currently, query_classifier is not linked to maxscale-common,
but executables must link to maxscale-common and query_classifier.

query_classifier/query_classifier.map

@@ -0,0 +1,20 @@
+{
+    global:
+        qc_end;
+        qc_get_affected_fields;
+        qc_get_canonical;
+        qc_get_created_table_name;
+        qc_get_database_names;
+        qc_get_operation;
+        qc_get_qtype_str;
+        qc_get_table_names;
+        qc_get_type;
+        qc_init;
+        qc_is_drop_table_query;
+        qc_is_real_query;
+        qc_query_has_clause;
+        qc_thread_end;
+        qc_thread_init;
+    local:
+        *;
+};