Revert "Implement xfer:libraries-svr4:read packet"

D62502, together with D62503 have broken the builds which have XML
support enabled. Reverting D62503 (r364355) fixed that, but has broken
has left some of the tests introduced by D62502 broken more or less
nondeternimistically (it depended on whether the system happens to place
the library list near unreadable pages of memory). I attempted to make a
partial fix for this in r364748, but Jan Kratochvil pointed out that
this reintroduces the problem which reverting D62503 was trying to
solve.

So instead, I back out the whole thing so we can get back to a clean
slate that works for everyone. We can figure out a way forward from
there.

This reverts r364748, r363772 and r363707.

llvm-svn: 364751