user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/ansi/musl-generic-math/nearbyint.c

@@ -0,0 +1,20 @@
+#include <fenv.h>
+#include <math.h>
+
+/* nearbyint is the same as rint, but it must not raise the inexact exception */
+
+double nearbyint(double x)
+{
+#ifdef FE_INEXACT
+	#pragma STDC FENV_ACCESS ON
+	int e;
+
+	e = fetestexcept(FE_INEXACT);
+#endif
+	x = rint(x);
+#ifdef FE_INEXACT
+	if (!e)
+		feclearexcept(FE_INEXACT);
+#endif
+	return x;
+}