[BUGFIX] T3editor: Honour fileDenyPattern on saving included TS

fileDenyPattern is only checked on loading so far.
Needs to be added for saving as well taken into account, since
otherwise an arbitrary file (including .php) can be overwritten.

Change-Id: Ia7edc83c8954942fb848746abc0980a304a1a6df
Resolves: #53195
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Reviewed-on: https://review.typo3.org/25046
Reviewed-by: Francois Suter
Tested-by: Francois Suter
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer