We weren't calling the method here before because it was ill-formed.
No start files meant that we got the front half of the init section but
not the back half (no 'ret' in _init!). Now that we have the proper
crtbeginS and crtendS files from libgcc to help us out, we can assume
that DSOs will have the proper _init method defined.
This patch also adds some missing relocation defines to exec_elf.h,
and a few helper classes/methods to ELFImage so that we can use it
for our dynamically loaded libs and not just main program images from
the kernel :)