Extend the crazy linker for arm64 packed relative relocations.
Add delta decoding for RELA relocations. Add a signed LEB128
decoder, and move LEB128 helper classes into their own header file.
Select either run length or delta decoding depending on the signature
found in the packed relocations section.
BUG=385553
Review URL: https://codereview.chromium.org/
477943002
Cr-Commit-Position: refs/heads/master@{#290542}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290542 0039d316-1c4b-4281-b951-d872f2087c98