The test case testsuite/libffi.call/many_win32.c can spuriously fail due
to excess floating-point precision. Instrumenting it with some printf
calls shows differences well above FLT_EPSILON. (Note when
instrumenting it that multiple computations of the difference, such as
one in a print and another in the conditional, may produce different
results.)
Rather than complicating the test suite with architecture-specific flags
to avoid excess precision, just simplify the floating-point computation
to avoid a dependency on potential excess precision.
