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/fmaxl.c

@@ -0,0 +1,21 @@
+#include <math.h>
+#include <float.h>
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double fmaxl(long double x, long double y)
+{
+	return fmax(x, y);
+}
+#else
+long double fmaxl(long double x, long double y)
+{
+	if (isnan(x))
+		return y;
+	if (isnan(y))
+		return x;
+	/* handle signed zeros, see C99 Annex F.9.9.2 */
+	if (signbit(x) != signbit(y))
+		return signbit(x) ? y : x;
+	return x < y ? y : x;
+}
+#endif