testsuite/libffi.call/many.c: Avoid spurious failure due to excess precision

The test case testsuite/libffi.call/many.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.
testsuite/libffi.call/many_win32.c: Avoid spurious failure due to excess precision

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.
ChangeLog: Document many.c and many_win32.c changes to avoid spurious failures
Merge pull request #88 from joshtriplett/such-precision-many-fail-wow

testsuite/libffi.call/many.c: Avoid spurious failure due to excess precision
testsuite: Remove fragile stack pointer checks

testsuite/libffi.call/closure_stdcall.c and
testsuite/libffi.call/closure_thiscall.c include inline assembly to save
the stack pointer before and after the call, and compare the values.
However, compilers can and do leave the stack in different states for
these two pieces of inline assembly, such as by saving a temporary value
on the stack across the call; observed with gcc -Os, and verified as
spurious through careful inspection of disassembly.
Merge pull request #91 from joshtriplett/esp-extra-stackery-perception

testsuite: Remove fragile stack pointer checks
ChangeLog: Document testsuite changes to remove fragile stack pointer checks
Merge pull request #94 from joshtriplett/esp-extra-stackery-perception

ChangeLog: Document testsuite changes to remove fragile stack pointer checks