i386: Use generic division to generate INEXACT exception

Introduce math_force_eval_div to use generic division to generate
INEXACT as well as INVALID and DIVZERO exceptions.

libgcc/ChangeLog:

	* config/i386/sfp-exceptions.c (__math_force_eval): Remove.
	(__math_force_eval_div): New define.
	(__sfp_handle_exceptions): Use __math_force_eval_div to use
	generic division to generate INVALID, DIVZERO and INEXACT
	exceptions.

libatomic/ChangeLog:

	* config/x86/fenv.c (__math_force_eval): Remove.
	(__math_force_eval_div): New define.
	(__atomic_deraiseexcept): Use __math_force_eval_div to use
	generic division to generate INVALID, DIVZERO and INEXACT
	exceptions.

libgfortran/ChangeLog:

	* config/fpu-387.h (__math_force_eval): Remove.
	(__math_force_eval_div): New define.
	(local_feraiseexcept): Use __math_force_eval_div to use
	generic division to generate INVALID, DIVZERO and INEXACT
	exceptions.
	(struct fenv): Define named struct instead of typedef.