[BUGFIX] Extension installer: Handle multiple blanks

The parser of the ext_tables.sql file removes double blanks
from the input line - but only once. So if there are multiple
blanks at least double blanks remain and irritate the later
comparison about whether the field definition is different.

Resolves: #62245
Releases: master,6.2
Change-Id: I6ab4cb543f5373916388567d3d9969c6681fa8e8
Reviewed-on: http://review.typo3.org/33841
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>