aesthetic fix: turn names of nanosleep args to lowercase
new lib: ctypes
take ssize_t and __off_t from ctypes
jack process callback uses static buffer for cmp + various buffer improvements

- buffers can be dynamic (appendable/resizable) or static

- removed size/capacity/data accessors for simplicity

- buffer_resize() and buffer_append() return the new capacity and the number of
  bytes appended (not buffer_t* as previously)

- new method: buffer_reset() sets size to 0

- ffi cdefs for cmp-buffer interop moved to buffer.lua (from msgpack.lua)

- fixed another memleak