[ticket/11438] Update sphinx.sample.conf to one provided by config_generate()

PHPBB3-11438
[ticket/11438] Move backslash to concatenate the query strings correctly

Was broken in 03d2c6413c25b1faf7f37ff20625ce986b19eb88

PHPBB3-11438
[ticket/11438] Add empty sql_query_pre to delta-source

PHPBB3-11438
[ticket/11438] Add helpful comments from sample config to ACP output

PHPBB3-11438
[ticket/11438] Add spaces after # comment start and before \ line breaks

PHPBB3-11438
Merge PR #1298 branch 'nickvergessen/ticket/11438' into develop

# By Joas Schilling
# Via Joas Schilling
* nickvergessen/ticket/11438:
  [ticket/11438] Add spaces after # comment start and before \ line breaks
  [ticket/11438] Add helpful comments from sample config to ACP output
  [ticket/11438] Add empty sql_query_pre to delta-source
  [ticket/11438] Move backslash to concatenate the query strings correctly
  [ticket/11438] Update sphinx.sample.conf to one provided by config_generate()