[ELF] - Lazy relocations support for x86 target.

Patch implements lazy relocations for x86.
One of features of x86 is that executable files and shared object files have separate procedure linkage tables. So patch implements both cases.

Detailed information about instructions used can be found in http://docs.oracle.com/cd/E19620-01/805-3050/chapter6-1235/index.html (search: x86: Procedure Linkage Table).

Differential revision: http://reviews.llvm.org/D14955

llvm-svn: 254098