[ELF] Support for PT_GNU_PROPERTY in header and tools

The PT_GNU_PROPERTY is generated by a linker to describe the
.note.gnu.property section. The Linux kernel uses this program header to
locate the .note.gnu.property section.

It is described in "The Linux gABI extension"

Include support for llvm-readelf, llvm-readobj and the yaml reader and
writers.

Differential Revision: https://reviews.llvm.org/D70959