idl: limit recurion on recursive elements

idl: limit recurion on recursive elements

Limit the max_recursion on self recursive definitions in the idl to
20,000. This value is hopefully large eneough to not impact normal
operation, but small eneough to prevent stack over flow issues.

Credit to OSS-Fuzz

REF: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19820
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14254

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Thu Feb 27 02:29:21 UTC 2020 on sn-devel-184