added backward compatibility symbols for libqc-opt.so

Change-Id: I196e913e642c25478933c9a873cd3198702ec0ae

Conflicts:
	common/utext.cpp

Change-Id: Ib5f3738db4625c3ce403e90f31c25d1c3f500d72
Add backward compatibility symbols for ICU 51 needed by libqc-opt.so

u_digit
utext_close
utext_openUChars
u_errorName

Change-Id: If3b2a1d31bbd6cb29ecb2fe402352c6a178892a3