Add libwilhelm to app_process.

If an app exposes new/delete from a shared library, the libwilhelm
shared library can wind up using the new from the app shared library,
and the delete from libc++. It is completely legal for the app to
export new/delete in this way, so in order to avoid this situation,
preload libwilhelm in the zygote. This forces libwilhelm to always
resolve the new/delete from libc++.

This library cannot be added to android_runtime since libwilhelm
has a shared library which depends on android_runtime.

Bug: 21032018
Change-Id: Id89c196df62d98d62855a1421f397b75a7e990a9