Remove some unused libm-test exception macros.

Remove some unused libm-test exception macros.

This patch removes some libm-test-support.h macros for exceptions that
are no longer used.  EXCEPTIONS_OK has been unused for some time.  The
macros for underflow exceptions with some types only were used when
the results for complex inverse trig and hyperbolic functions were
manually maintained, but are no longer needed now the auto-libm-test
machinery is used to determine the correct result and exceptions for
every floating-point format and rounding mode.

Tested for x86_64.

	* math/libm-test-support.h (EXCEPTIONS_OK): Remove macro.
	(UNDERFLOW_EXCEPTION_FLOAT): Likewise.
	(UNDERFLOW_EXCEPTION_OK_FLOAT): Likewise.
	(UNDERFLOW_EXCEPTION_DOUBLE): Likewise.
	(UNDERFLOW_EXCEPTION_OK_DOUBLE): Likewise.
	(UNDERFLOW_EXCEPTION_LDOUBLE_IBM): Likewise.