An easy to use, portable, high resolution cycle counter
=======================================================

Matteo Frigo and Steven Johnson implemented a portable high resolution
cycle counter in fftw3.  The cycle counter is so useful that it has
its own section in the fftw download page:

    http://www.fftw.org/download.html

It checks the macros generated by autoconf to choose the most accurate
counter on different platforms.

Not everyone is familiarly with autoconf; or sometimes it is just
overkill to use autoconf for a small project.  Therefore, I merge
"cycle.h" into a "configure.ac" file.  I then wrote a simple script
`bootstrap` that runs autoconf and sticks the `configure` script and
`cycle.hin` together.

The resulting `mkcycle` scrip will check the system and produce the
header file "cycle.h".  Also, take a look at the very simple example
"test.c" which shows using a for-loop to copy array of double is
usually faster than using memcpy().