mysql_backend.c, mysql_client.c free error message GWBUF after calling handleError
readconnroute.c:handleError send error message to client before returning.
readwritesplit.c:handleError don't free error message buffer anymore since the caller of handleError frees it.
mysql_common.c:gw_send_change_user_to_backend creates new authentication message which is to be sent to backend. GWBUG type flags were not copied from original GWBUF to new one. Thus the information that this is a session command was lost and it was processed in a wrong way. Especially replies were all routed back to client which caused misbehavior.
readwritesplit.c:execute_sescmd_in_backend didn't set GWBUF_TYPE_SESCMD type to GWBUF the command is in. Thus reply wasn't processed properly. Instead all replies were sent to client.
buffer.c:gwbuf_make_contiguous: when new buffer is created, copy original buffer's type to new buffer
modutil.c:modutil_replace_SQL: when new bugger is added to GWBUF, copy original buffer's type to new buffer
In all filters, merge all buffers of GWBUF to one before calling modutil:extract_SQL
Also changed 'authorization failed' to 'access denied'
mysql_common.c: fixed memory leak in gw_receive_backend_auth, and replaced error code '2800' with '28000'.
readconnroute.c:handleError didn't set *succp pointer so uninitialized value was used in caller's context.
makefile.inc: added -lm to linker flags
mysql_backend.c: added a few comments
query_classifier.cc: added function for printing combined query type from a bit field.
query_classifier.h: identify query types SHOW DATABASE, and SHOW TABLES to make log entries more understandable.
mysql_common.c: moved some trace log commands to debug log.
readwritesplit.c: moved some trace logs to debug log, added trace log commands to gather routing, query type and session information to one log entry.
skygw_debug.h: added string macros for several query and hint types.
Execution of session commands failed because session commands and normal sql statements were executed in a wrong order if backend was executing previous session command while new sql stmt was routed to that backend. There was a window where ordering went wrong.
It is possible that one normal sql stmt arrives while previous sescmds are still being executed.
Introduced a new member in backend_ref_t structure, bref_pending_cmd where new sql stmt pointer is stored in that case. When sescmds are executed completely, that command is automatically executed next.
