[toolchain/eglibc] add patch for eglibc version 2.15

This patch partially reverts an (e)glibc commit
which fixed a memory leak, however introduced lookup
errors in dlopen() with resulting segmentation faults
in certain scenarios.

References:
 - http://comments.gmane.org/gmane.comp.lib.glibc.user/1227
 - http://sourceware.org/ml/libc-alpha/2011-06/msg00006.html

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37029 3c298f89-4303-0410-b956-a3cf2f4a3e73