[ticket/12710] Prepare get_existing_indexes() for other DBMS

PHPBB3-12710
[ticket/12710] Fix changing the column type on oracle

PHPBB3-12710
[ticket/12710] Correctly fetch unique and normal indexes only in MSSQL

PHPBB3-12710
[ticket/12710] Fix problems with creating unique indexes on oracle

PHPBB3-12710
[ticket/12710] Fix "ORA-00972: identifier is too long [972]" on oracle

PHPBB3-12710
[ticket/12710] Correctly select index name and compare to column name

PHPBB3-12710
[ticket/12710] Can not use upper in oracles where claus

PHPBB3-12710
[ticket/12710] Remove table_name from index_name before deleting and recreating them

PHPBB3-12710
[ticket/12710] Do not try to match the uniqueness in the query

PHPBB3-12710
[ticket/12710] Compare to uppercase version

PHPBB3-12710
[ticket/12710] Fix foreach generation

PHPBB3-12710
[ticket/12710] Pass the original column data to the create function

PHPBB3-12710
[ticket/12710] Prefix column so it does not start with a number

PHPBB3-12710
[ticket/12710] Fix missing closing bracket

PHPBB3-12710
Merge remote-tracking branch 'github-nickvergessen/ticket/12710' into develop-ascraeus

* github-nickvergessen/ticket/12710:
  [ticket/12710] Fix missing closing bracket
  [ticket/12710] Prefix column so it does not start with a number
  [ticket/12710] Pass the original column data to the create function
  [ticket/12710] Fix foreach generation
  [ticket/12710] Compare to uppercase version
  [ticket/12710] Do not try to match the uniqueness in the query
  [ticket/12710] Remove table_name from index_name before deleting and recreating them
  [ticket/12710] Can not use upper in oracles where claus
  [ticket/12710] Correctly select index name and compare to column name
  [ticket/12710] Fix "ORA-00972: identifier is too long [972]" on oracle
  [ticket/12710] Fix problems with creating unique indexes on oracle
  [ticket/12710] Correctly fetch unique and normal indexes only in MSSQL
  [ticket/12710] Fix changing the column type on oracle
  [ticket/12710] Prepare get_existing_indexes() for other DBMS