add missing float.h macros

actually FLT_ROUNDS needs to expand to a static inline function that
obtains the current rounding mode and returns it, but that will be
added later with fenv.h stuff.

arch/i386/bits/float.h

+#define FLT_ROUNDS 1
+#define FLT_EVAL_METHOD 2
+
 #define LDBL_MIN     3.3621031431120935063e-4932L
 #define LDBL_MAX     1.1897314953572317650e+4932L
 #define LDBL_EPSILON 1.0842021724855044340e-19L

arch/x86_64/bits/float.h

+#define FLT_ROUNDS 1
+#define FLT_EVAL_METHOD 1
+
 #define LDBL_MIN     3.3621031431120935063e-4932L
 #define LDBL_MAX     1.1897314953572317650e+4932L
 #define LDBL_EPSILON 1.0842021724855044340e-19L