softmmu: add helper function to pass through retaddr

softmmu: add helper function to pass through retaddr

This patch introduces several helpers to pass return address
which points to the TB. Correct return address allows correct
restoring of the guest PC and icount. These functions should be used when
helpers embedded into TB invoke memory operations.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150710095650.13280.32255.stgit@PASHA-ISP>
Signed-off-by: Richard Henderson <rth@twiddle.net>