Relocatable kernel support for x86

This feature (enabled with CONFIG_RELOCATABLE) isn't very noticeable 
for end-users but it's quite interesting from a kernel POV(point of 
view). Until now, it was a requeriment that a i386 kernel was loaded 
at a fixed memory address in order to work, loading it in a different 
place wouldn't work. This feature allows to compile a kernel that can be 
loaded at different 4K-aligned addresses, but always below 1 GB, with no 
runtime overhead. Kdump users (a feature introduced in 2.6.13 that it triggers 
kexec in a kernel crash in order to boot a kernel that has been previously 
loaded at a 'empty' address, then runs that kernel, saves the memory where 
the crashed kernel was placed, dumps it in a file and continues booting the 
system) will benefit from this because until now the "rescue kernel" need to 
be compiled with different configuration options in order to make it bootable 
at a different address. With a relocatable kernel, the same kernel can be boot 
at different addresses.