[tests] Drop support for separate "make test"

If prove doesn't exist then "perl" doesn't really substitute since it
will only execute one test file.
[tests] Basic test case for pipeif (fails) and starting implementation
Adding some debug output to noop to help test pipeif
pipeif echos parts of a HTTP message to pipe or stdout

Known bug: buffering and concurrency issues means the order of header &
body can be swapped. Test checks for this (expected fail)
Bigger buffer better
Urgh. F_NOCACHE not only doesn't do what I want it's OSX only