[2.23] Support decoding of symbols for plt entries on arm

See f9dadca89a4a993e5c68137b5b162b5e79fa4455 and
fa1f1a225fd4598b2fb6edf4bf63591c9e72d13a

Change-Id: Ib5c17cc7e65989fe962ecb96e0ea8b6cf2aa5651

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Sat Apr 6 18:18:27 2013 +0800
[2.23] Provide __executable_start for PIE

See e84d2df4e4d8a96c78d8f738a6a1754343d61038
and 0bacab67d884144f0f0701359c481a6f0749f1f3

Change-Id: Iff854f6d77e859c83a287810c7dc666cf8a70878

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Sat Apr 6 18:28:08 2013 +0800