Check that the timeout value is in range.
Revert 78dac6e37943d1ad99841898806ea60b0eede636 and resolve a2478 in a way that avoids truncating snmpTargetAddrTimeout.
snmpd: Refactor init_kmem()

This patch does not change any functionality.
CHANGES: BUG: 2476: snmpd fails to start on AIX

On an AIX system there is no <kvm.h> header file nor do the /dev/dmem
or /dev/drum devices exist and hence DMEM_LOC is not defined. Avoid
that init_kmem() fails in that case.
CHANGES: AIX: Make tcp-mib build
CHANGES: AIX: Make udp-mib build
Fix netsnmp_ipaddress_ipv4_prefix_len to take an argument in network byte order as dokumentet