benchtests: Add fmax/fmin benchmarks

benchtests: Add fmax/fmin benchmarks

This patch adds fmax and fmin benchtests.  It is based math/s_fmax_template.c
implementation which checks for basically four different classes:

  1. if x is greater or equal than y.
  2. if x is less than y.
  3. if x or y is signaling.
  4. if y is nan.

Cases 1 and 2 are used for default input number (by mixing normal double
numbers and infinity), while case 3 and 4 are used each for on for a
benchmark class.

Checked on x86_64-linux-gnu and powerpc64-linux-gnu.

	* benchtests/Makefile (bench-math): Add fmin and fmax.
	(CFLAGS-bench-fmax.c): New rule.
	(CFLAGS-bench-fmin.c): New rule.
	* benchtests/fmax-inputs: New file.
	* benchtests/fmin-inputs: Likewise.