query_classifier.cc:skygw_get_canonical: if the item to be replaced is an empty string "", it is processed differently from the other cases due to difficulties to get wanted result by adding special rule for that to regex.
query_classifier.h: added parsing information structure to query classifier away from buffer.h.
buffer.c:introduced a buffer object which includes object pointer and a clean-up call-back function. Buffer objects form a list which is cleaned up by the last referrer of the buffer, as a part of gwbuf_free. Buffer object list is protected by a spinlock gwbuf_lock.
	Also added identifier type, bufobj_id_t which is enumerated type and currently includes one value only, GWBUF_PARSING_INFO. Added also a bitfield for information about the buffer. It currently has one type only, GWBUF_INFO_PARSED indicating that buffer content is parsed and there is buffer object of type GWBUF_PARSING_INFO.
skygw_utils.cc:replace_literal:changed regexec matching to case insensitive because user-defined literals are sometimes converted to upper-case ones.
canonical query tests for query classifier
the errmsg.sys file is now copied during test building
Merge pull request #30 from skysql/canonical_query_tests

Canonical query tests
more test cases for canonical queries and makefile typo fixes
query_classifier.cc:parsing_info_done: calling mysql_thread_end caused segfauls when same thread tried next time call free_embedded_thd because thread's sysvar was set to NULL in mysql_thread_end.
Added a few lines to canonical query test's input script which are not handled correctly.
Merge branch 'MAX-160' of https://github.com/skysql/MaxScale into MAX-160

Conflicts:
	query_classifier/test/canonical_tests/input.sql
skygw_utils.cc:replace_literal: Fixed regular expression which, for example,  accepted "200" with needle "2"
query_classifier.cc: fixed invalid argument list in logging command.
input.sql: added a few previously failed cases for canonical query test
Added expected results for missing queries.
Merge remote-tracking branch 'maxscale/MAX-160' into dev
changed mqfilter option syntax and added multiple users and hosts to the source-based logging trigger