Explore other profilers supported by gprof2dot

• axe
• callgrind
• hprof -- JAVA
• json -- dunno!
• oprofile -- doesn't work in VM: "Your kernel's Performance Events Subsystem does not support your processor type."
• perf -- doesn't install on 22.10 see #38
• prof -- original and best
• pstats -- python
• sleepy -- Windows only
• sysprof
• xperf
• dtrace