Fix math/test-nearbyint-except for no-exceptions configurations.

The test math/test-nearbyint-except conditions some of its tests on an
EXCEPTION_TESTS call, not not all that need such a condition.  This
patch fixes it to use such a conditional for all its tests and to
return 77 (UNSUPPORTED) if none of the floating-point types tested
support exceptions.

Tested for mips64 soft float (where the test previously failed and is
now UNSUPPORTED); also tested for x86_64 to make sure the test still
PASSes in exceptions-supported cases.

	* math/test-nearbyint-except.c: Include <stdbool.h>.
	(any_supported): New variable.
	(TEST_FUNC): Return early if !EXCEPTION_TESTS (FLOAT).  Otherwise
	set any_supported.
	(do_test): Return 77 if no floating-point type supported
	exceptions.