User grants debug Mysql part: retrieve IS_GRANTABLE + update column privs

(See http://dev.mysql.com/doc/refman/5.6/en/grant-table-structure.html
Table 6.7. Set-Type Privilege Column Values Section)

Change-Id: I6173ba0df84f722a872afa59d7d7dc9eefe3e368
Reviewed-on: https://gerrit.libreoffice.org/7155
Reviewed-by: Lionel Elie Mamane <lionel@mamane.lu>
Tested-by: Lionel Elie Mamane <lionel@mamane.lu>