add --vips-profile

only added a few gates so far, try a visualiser next
parse profile output
stuff
Merge branch 'master' into gate
Merge remote-tracking branch 'origin/gate' into gate
Merge branch 'master' into gate
cleanups, vipsprofile.py now works
start adding cairo output
Merge remote-tracking branch 'origin/master' into gate
now draws something
txt rendering
works!
support main thread gates
add lots of instrumentation

also svg output
more calcs in output