ARM EABI: add new helper functions resp. function names

The ARM EABI defines new names for GCC helper functions,
and GCC seems to need some new functions as well.

This patch is a minimal-invasive approach to fix problems with EABI
conformant tool chains (to be used with "USE_PRIVATE_LIBGCC=yes").

Signed-off-by: Wolfgang Denk <wd@denx.de>
Tested-by: Dirk Behme <dirk.behme@googlemail.com>