Added phdr upper bound checks to ElfObject.

Ensure the program_headers call will fail correctly if the program
headers are larger than the underlying buffer.

Patch by Parker Thompson!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315012 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed