Made timeout_state and timeout_interval universal

I cannot find one instance where more than one of each of these globals
are needed:

timeout_state
timeout_interval

Previously, three seperate variables existed:

socket_timeout_state
timeout_state
runcmd_timeout_state

timeout_interval
socket_timeout
runcmd_timeout

I presume that at some point someone planned on using a few different
timeouts in a plugin.  As no plugin currently relies on this behavior as
far as I can tell, and as optarg will only let the user configure one
set, I decided to change all instances of these two vars to:

timeout_state
timeout_interval

This makes it easy to add just one parse_timeout_string function to
utils.c

I also noticed that runcmd.h did not include utils.h, but that all
plugins using runcmd.h also included utils.h.  I added utils.h to
runcmd's includes so that the global variables altered by the parse
function would be seen by the alarm handler in runcmd.c.

Let me know if anyone forsees any issues with these changes.

Still unresolved issues with timeout_intervals and check_snmp and a few
of the ntp plugins.