New BIONIC_L(Android-L) has own support for STPCPY

The new BIONIC for android L preview has own support for STPCPY for all
arches. This patch removes inbuilt STPCPY support from busybox when BIONIC_L
is defined.

Change-Id: I189a4489450ca11eddd5b3f49a29f1fe46d0157a
Merge remote-tracking branch 'cm/cm-11.0' into HEAD