Simplify simple tests check and correct wrong value checks

  The new comparison tests on check/test are based on check/math
comparison tests.
  The wrong value checks are tests on sign on the wrong pointer,
most times harmless but could lead to a segfault on special
conditions. These should be temporary, as it should soon be
changed to use the ovm_xyz functions to fold constants.
Remove workaround to x87 problem and off by one error.

  The x87 issue was needing to call jit_retval_d to avoid a reproducible
but unexpected SIGSEGV, that was "corrected" by adding an emms call before
calling C functions from lightning, to "clear" the x87 stack.
  The off by one error was in debug output of nan_p and inf_p, that was
printing a nul character.