I've committed a bunch more changes to simplify and speed up ld.elf_so
a little.  (See source-changes for details.)

I've tested 8 of the 9 currently-supported CPU types; however, I am
unable to test VAX at the moment.  I suspect that it may fail.  If it
does fail, it will probably need to implement an early self-relocate
function like other platforms do.