Add constant time buf_compare_ct function

This patch adds a constant time memory compare function that mitigates
timing attacks. This patch also fixes three locations where this could
be a problem.

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
add README.md

Change-Id: I65feab3957dea0ae7c246f4fb9cc0bae82297d20
Signed-off-by: Cedric Chaumont <cedric.chaumont@st.com>
Update aeabi_divmod.c

On behalf of Herve Sibert (hsibert)
    Corrected division_qr to work on unsigned ints, and simplified
    uint_div_qr accordingly
    Note - this file is no longer ARM-specific.

It fixes #2 (GitHub issue)