libez: start turning flibc into libez.

The goal of this renaming is to change the function names: every
function will now have a prefix, to respect the usual way to deal
with namespaces in C.

We randomly picked a new name: ez (eazy).
It's a short prefix, and it represents well what the library offers:
simple functions for everyday use.

Enjoy !
Rename log and vt102.
Hide symbols from vt102 header.

See 'How To Write Shared Libraries', Ulrich Drepper,
http://www.akkadia.org/drepper/dsohowto.pdf
2.2.3 Define Per-Symbol Visibility
io.c: rewrite file, add more functions.
list: renamed to ez_list.
unit: renamed to ez_test.
math: renamed to ez_math.
str: renamed to ez_str.
flic: renamed to libez.
Add missing io.h.