trace var for TCL_TRACE_READS ?

[michaelortmann]

Currently eggdrops code is full of variable tracings for: TCL_TRACE_READS | TCL_TRACE_WRITES | TCL_TRACE_UNSETS the tracing functions mostly (or all?) are only interested if a var is set or changed there is no need to run thru those functions for TCL_TRACE_READS lets safe carbon emissions / electricity and remove the TCL_TRACE_READS where it is not needed.