1) Proper emit displacements for x86, using absolute relocations where necessary

1) Proper emit displacements for x86, using absolute relocations where necessary
for ELF to work.
2) RIP addressing: Use SIB bytes for absolute relocations where RegBase=0,
IndexReg=0.
3) The JIT can get the real address of cstpools and jmptables during
code emission, fix that for object code emission

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78129 91177308-0d34-0410-b5e6-96231b3b80d8