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

llvm-svn: 78129