uClibc: Fix threaded use of res_ functions.

This patch moves res_init() back above #undef _res. It fixes dns resolving issue in OpenWrt
(uClibc related - OpenWrt ticket #11929). It is a backport from uClibc master.

Further details are there:
http://git.uclibc.org/uClibc/commit/libc/inet/resolv.c?id=20b69920b299585265eb100d0b67e1097ccb1092



Signed-off-by: Jiri Slachta <slachta@cesnet.cz>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39177 3c298f89-4303-0410-b956-a3cf2f4a3e73