Change some ELF utils to return the length as a size_t.

R=mark@chromium.org

Review URL: https://breakpad.appspot.com/7694002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1349 4c0a9323-5329-0410-9bdc-e9ce6186880e
Add frame pointer recovery to the AMD64 Stackwalker.

BUG=https://code.google.com/p/chromium/issues/detail?id=393594
R=mark@chromium.org

Review URL: https://breakpad.appspot.com/10664002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1350 4c0a9323-5329-0410-9bdc-e9ce6186880e