link-grammar: update to 5.9.1

Version 5.9.1 (28 April 2021)
* Fix build break when SQLite3 is not installed. #1195

Version 5.9.0 (25 April 2021)
* Use #define for custom configuration in dictionaries. #1128
* Panic-mode fixes and extensions. In link-parser see !help panic_variables.
* English dict: fix silly mistake with "I love cats and dogs".
* Disable maintainer-mode in `configure.ac`.
* Fix very rare crash/corruption introduced in v.5.8.1 #1142
* English dict: fix problems with "just/only".
* English dict: work on hesitation markers.
* Fix multi-threading mem-leak. #1149
* Provide emscripten javascript wrapper for the command-line parser.
* Public API shared library entry points exported automatically. #1182
* Provide bindings for the Vala programming language.
* Increase number of allowed idiom expressions. #1187
* Replace O(n^2) idiom loading algo by an O(n log n) algo. #1194
* Disable SAT solver by default.
* New tool: Sentence generator! This is an experimental prototype.

(gutteridge)