Pg-query

* Clean up includes to avoid dependency on stdbool.h and xlocale.h
* Change PL/pgSQL input to be the full CREATE FUNCTION statement
* This is necessary for parsing, since we need the argument and return types
* Fingerprinting Version 1.1
* Only ignore ResTarget.name when parent field name is targetList *and*
we have a SelectStmt as a parent node (fixes UpdateStmt fingerprinting)
* Normalize the password in ALTER ROLE ... PASSWORD '123' statements
* Make library thread-safe through thread-local storage [13](https://github.com/lfittl/libpg_query/issues/13)

* Extract source code using LLVM instead of manually compiling the right objects
* This speeds up build times considerably since we don't download the Postgres
source anymore, instead shipping a partial copy created as part of a release.
* Experimental support for parsing PL/pgSQL source code (output format subject to change)

* Make sure we encode special characters correctly in JSON output ([zhm](https://github.com/zhm) [11](https://github.com/lfittl/libpg_query/pull/11))

* Fix stack overflow when parsing CREATE FOREIGN TABLE ([9](https://github.com/lfittl/libpg_query/issues/9))
* Update to PostgreSQL 9.5.3

* Add pg_query_fingerprint() method that uniquely identifies SQL queries,
whilst ignoring formatting and individual constant values
* Update to PostgreSQL 9.5.2