Added new socketoptions to force the isotp protocol to intentionally

Added new socketoptions to force the isotp protocol to intentionally
misbehave for regression tests.

CAN_ISOTP_TX_STMIN:
Set a value in nano secs that's used as minimum CF gap by the sender.
This value is used instead of the value provided by the receiver inside the FC.

CAN_ISOTP_RX_STMIN:
Ignores received CF frames which timestamps differ less than this value in nano
secs. This is used to test the receivers misbehaviour when the receiver
provides a lower stmin value that he's able to cope with. Received CF frames
are silently dropped when they come faster than specified by this value.

git-svn-id: svn://svn.berlios.de//socketcan/trunk@1201 030b6a49-0b11-0410-94ab-b0dab22257f2