math: Properly cast X_TLOSS to float [BZ #28713]

Add

 #define AS_FLOAT_CONSTANT_1(x) x##f
 #define AS_FLOAT_CONSTANT(x) AS_FLOAT_CONSTANT_1(x)

to cast X_TLOSS to float at compile-time to fix:

FAIL: math/test-float-j0
FAIL: math/test-float-jn
FAIL: math/test-float-y0
FAIL: math/test-float-y1
FAIL: math/test-float-yn
FAIL: math/test-float32-j0
FAIL: math/test-float32-jn
FAIL: math/test-float32-y0
FAIL: math/test-float32-y1
FAIL: math/test-float32-yn

when compiling with GCC 12.

Reviewed-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>