Support Linux cross-arch injection in the native drdeploy frontends

This required adding an architecture parameter to
get_config_val_other_app() and detecting the bitwidth of the exe in
drinjectlib.

Also add support for the -dr_home alias used by the Linux suite to test
cross-arch injection.

Review URL: https://codereview.appspot.com/7351043

git-svn-id: https://dynamorio.googlecode.com/svn/trunk@1927 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6