ELF: Add .eh_frame 'P', 'R' and 'L' augmentation characters.
ELF: Add .eh_frame 'P', 'R' and 'L' augmentation characters.

This basically reverts commit r260073 because it is found that
augmentation strings don't always start with "zR". It is reported
as https://llvm.org/bugs/show_bug.cgi?id=26541.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@260294 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld