Bionic: Make DISALLOW_COPY_AND_ASSIGN conditional

Make the definition of DISALLOW_COPY_AND_ASSIGN conditional. This is
so that the projects that include libnativehelper and bionic macros
do not have to be careful in which order those projects are included.

Bug: 18334516
Change-Id: Ib12a2c2b7ad2e360edcf3b26cb1be626540fadc1
Merge "Bionic: Make DISALLOW_COPY_AND_ASSIGN conditional"