Fixes IP address used as indices

While trying to implement ipCidrRouteTable for an
internal project, I came upon a problem on the way
parse_one_oid_index handles IP addresses.

It reads too many numbers, finaly getting a wrong IP
address.
However the fix is very simple.
Just change line 3314 in snmplib/mib.c from:

for (i = 0; i < *oidLen; ++i) {

to

for (i = 0; i < 4 && i < *oidLen; ++i) {

and this is fixed. Not even worthy of a patch file (I
am to lazy to create a patch file 8).

My email address is arvanit@ellemedia.com