This patch adds logging macros:

RING_XERR
RING_XWARN
RING_XINFO
RING_XDBG

Acting like thus w/o 'X' but w/o a linefeed at end of message.

Change-Id: Ia4505e25354bbe2d6ddd96992e4f2f906025aa86
Tuleap: #547