docs/probe_math_exception.c:

docs/probe_math_exception.c:
	update example
libc/sysdeps/linux/i386/bits/mathinline.h:
	improve __finite() macro, add __finitef macro
	(why they aren't always macros? why aren't they arch independent?)
libm/math_private.h:
	much better comments on math_opt_barrier() and math_force_eval()
libm/s_finite[f].c:
	improve out-of-line __finite[f]() too (one byte less, yay...)