Debugged another gcc testsuite failure, and found that tbnz/tbz are
broken when the bit position to test is greater than 31.  There are
two problems.  The high bit of the bit position is shifted left by the
wrong amount.  And we need to use (uint64_t)1 to get a 64-bit shift
result.

Tested with a gcc C testsuite run.  This reduces failures from 2856 to 2710.

Jim