Imported Mike Pall's experimental tporf.lua and vmprof.c.

tprof.lua is a simple application profiler written in Lua.
Example:
  snabbswitch -l jit.tprof -e 'jit.tprof.on()' -l selftest -e 'jit.tprof.off()'

vmprof.c is a hardcore runtime system profiler written in C.
I haven't worked out how to use it yet :-)