handle/copyable: Implement copyable handle

This is a generic handle type that holds a resource and uses RAII to
call a user defined function when the resource is copied or destroyed.

Tested:
    Built and run through unit tests.

Change-Id: I3d23544b2e7c8d8c6686effc03b3b7433ea18bf5
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/.gitignore b/.gitignore
index 4524a76..f58f9f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,5 +41,6 @@
 /src/stdplus.pc
 
 # Output binaries
+/test/handle/copyable
 /test/handle/managed
 /test/signal