Start on -native_exec_retakeover by hooking _dl_runtime_resolve

The current hook does nothing except forward the resolution calls forwards to
the loader.

Inserting the hook requires checking PT_GNU_RELRO and making that region
temporarily writable.

Later, we can check to see if the resolved address is in another module and
replace it with our own stub that enters DR.

Review URL: https://codereview.appspot.com/7237067

git-svn-id: https://dynamorio.googlecode.com/svn/trunk@1876 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6