Fix math/test-fenvinline for no-exceptions configurations.

This patch fixes math/test-fenvinline.c to stop it failing in
no-exceptions configurations (where some exception macros are defined
but may not be supported at runtime).  The relevant parts of the test
are disabled in that case; some parts can still run (and the rounding
mode tests are written in a way such that they work even if the
rounding modes aren't supported).

Tested for mips64 soft-float, and for x86_64 to make sure the tests
still run when the exceptions are supported.

	* math/test-fenvinline.c (do_test): Disable tests of raised
	exceptions if !EXCEPTION_TESTS (FLOAT).