#2806 stack related crash on Windows

[Joe Mistachkin]

proc test { a } { regsub -all -- {^(.*)$} $a {abc\0def}
result; return [test $result] }; test "this is cool."

The above script can successfully crash TDK 3.1 (Tcl
8.4.6) on Windows.

I believe that the stack checking threshold on Windows
may need to be adjusted to compensate for the regexp
engine's extensive use of the stack.

[Jeffrey Hobbs]

Logged In: YES
user_id=72656

This does not crash 8.4.8-RC, so someone must have updated
the threshhold.