IVGCVSW-6077 Add the Custom Memory Allocator interface definition

 * Added ICustomAllocator.hpp to include/armnn/backends/
 * Added the ability to specify an ICustomAllocator to the CreationOptions


Signed-off-by: David Monahan <david.monahan@arm.com>
Change-Id: I820e468b691aa032c9bd2c1e1257dc9d02f981d9
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b4e0a38..13d3937 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -163,6 +163,7 @@
     include/armnn/DescriptorsFwd.hpp
     include/armnn/Exceptions.hpp
     include/armnn/backends/ILayerSupport.hpp
+    include/armnn/backends/ICustomAllocator.hpp
     include/armnn/IAsyncExecutionCallback.hpp
     include/armnn/ILayerVisitor.hpp
     include/armnn/INetwork.hpp