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/llrintl.c

@@ -0,0 +1,36 @@
+#include <limits.h>
+#include <fenv.h>
+#include "libm.h"
+
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long long llrintl(long double x)
+{
+	return llrint(x);
+}
+#elif defined(FE_INEXACT)
+/*
+see comments in lrint.c
+
+Note that if LLONG_MAX == 0x7fffffffffffffff && LDBL_MANT_DIG == 64
+then x == 2**63 - 0.5 is the only input that overflows and
+raises inexact (with tonearest or upward rounding mode)
+*/
+long long llrintl(long double x)
+{
+	#pragma STDC FENV_ACCESS ON
+	int e;
+
+	e = fetestexcept(FE_INEXACT);
+	x = rintl(x);
+	if (!e && (x > LLONG_MAX || x < LLONG_MIN))
+		feclearexcept(FE_INEXACT);
+	/* conversion */
+	return x;
+}
+#else
+long long llrintl(long double x)
+{
+	return rintl(x);
+}
+#endif