add CLICK_COLD #define for rarely used functions

Signed-off-by: Cliff Frey <cliff@meraki.com>
Mark many initialization-related functions as COLD

This was done by running
    sed -i -r -e 's/\b(configure\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b(initialize\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b(add_handlers\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b(cleanup\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b(read_param\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b(write_param\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/^( *[A-Z][a-zA-Z]+\(\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/^( *~[A-Z][a-zA-Z]+\(\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
    sed -i -r -e 's/\b([a-z_]*(write|read)_handler\(.*\));/\1 CLICK_COLD;/' `find elements/ -name '*.hh'`
and then manually fixing up directiplookup.hh

On some workloads at Meraki, we have seen bad performance caused by
instruction TLB misses.  This change drastically reduces the number of
instruction TLB misses on those workloads, leading to ~30% faster
performance (as measured on a powerpc 44x machine).

Signed-off-by: Cliff Frey <cliff@meraki.com>
test: add a simple performance test

I added this hoping for it to show that the CLICK_COLD change made a
noticable performance different on x86.  However, I could not get it to.
It may be that I need more unique click elements in order to put the
instruction TLB under more pressure.

Signed-off-by: Cliff Frey <cliff@meraki.com>