make libacc run with execute stack protections enabled.

libacc was allocating memory using malloc for executable pages.
When running on a system where the stack and heap are not
executable, using malloc for executable pages will result in
a segfault.

This change modifies libacc to allow the code to run, even
if the system is running with executable stack and heap disabled.

Change-Id: Ia74e3d83750c09b7eefd865ff059db920093040d