[TASK] Add information to INSTALL.txt about ThreadStackSize

With the large regular expressions in Fluid Apache on Windows might
run out of stack space. The default stack size on Windows is only
1MB compared to 8MB default on *nix.
Add extra information in INSTALL.txt to explain this.

Change-Id: I259f36d8793ee82f96f4cb01f20880daec322f27
Releases: 6.0
Fixes: #41998
Reviewed-on: http://review.typo3.org/15617
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel