lib/libm_dbl: Support FLT_EVAL_METHOD == 16.

That's almost the same as FLT_EVAL_METHOD == 0, but indicates the
presence of _Float16_t support.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

lib/libm_dbl/rint.c

@@ -2,7 +2,7 @@
 #include <math.h>
 #include <stdint.h>
 
-#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1 || FLT_EVAL_METHOD==16
 #define EPS DBL_EPSILON
 #elif FLT_EVAL_METHOD==2
 #define EPS LDBL_EPSILON