Documentation fixes

* amqp.h: Fix link to amqp_destroy_envelope()
* amqp_ssl_socket.h: Fix typo in parameter name
* amqp_tcp_socket.h: Use correct parameter name
amqp.h: Typo in amqp_basic_ack() documentation
Table field kind fixes

* Bugfix: short-int has kind 'U', not 's'
* Bugfix: kinds 'L' and 'l' were swapped
* Added: short-string kind ('s')
* Deprecated: name UTF8 in favour of LONGSTRING
* Added: nonconformance warning for byte string kind ('x')
* Updated table test accordingly
Merge branch 'feature-field-kind' into local-develop
Merge branch 'feature-docfix' into local-develop