[ELF] - Added support of PT_OPENBSD_RANDOMIZE

This is 30646.

PT_OPENBSD_RANDOMIZE
The array element specifies the location and size of a part of the memory image of the program that must be filled with random data before any code in the object is executed. The memory region specified by a segment of this type may overlap the region specified by a PT_GNU_RELRO segment, in which case the intersection will be filled with random data before being marked read-only.

Reference links:
http://man.openbsd.org/OpenBSD-current/man5/elf.5
https://github.com/openbsd/src/commit/c494713c450d98da3f2e1451ee8c7fb675a7c461

Differential revision: https://reviews.llvm.org/D25469

llvm-svn: 284234