function: LOC function implementation

[mcuadros]

This PR introduces the https://github.com/hhatto/gocloc through a new LOC function returning a JSON struct.

SELECT    
    LANGUAGE(file_path, blob_content) as lang,     
    SUM(JSON_EXTRACT(LOC(file_path, blob_content), '$.Code')) as code,  
    SUM(JSON_EXTRACT(LOC(file_path, blob_content), '$.Comments')) as comments,     
    SUM(JSON_EXTRACT(LOC(file_path, blob_content), '$.Blanks')) as blanks,    
    COUNT(1) as files 
FROM commit_files 
NATURAL JOIN refs 
NATURAL JOIN blobs 
WHERE ref_name='HEAD' 
GROUP BY lang;

+------+------+----------+--------+-------+
| lang | code | comments | blanks | files |
+------+------+----------+--------+-------+
| Markdown | 63763 |        0 |  24316 |   693 |
| YAML | 6033 |       91 |    788 |   229 |
| Text |    0 |        0 |      0 |   437 |
| Go   | 7444446 |   857226 | 638471 | 18639 |
|      |    0 |        0 |      0 |  1272 |
| Ignore List |    0 |        0 |      0 |   177 |
| TOML | 3616 |       37 |    512 |    32 |
| Dockerfile |    0 |        0 |      0 |    35 |
| C    | 1564 |      277 |    431 |    27 |
| Makefile | 5084 |     5544 |   1255 |   319 |
| Groovy |   61 |        0 |      0 |     1 |
| SQL  | 1198 |        0 |      6 |    46 |
| Protocol Buffer |    0 |        0 |      0 |   810 |
| JSON | 23245 |        0 |      0 |   223 |
| HTML | 14597 |      814 |   2390 |   116 |

[ajnavarro]

Could you add some examples into the documentation please?