user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/tests/ansi/alloc.c

@@ -0,0 +1,39 @@
+#include <stdlib.h>
+#include <assert.h>
+#include <stdint.h>
+#include <errno.h>
+
+int main() {
+	void *p;
+
+	p = aligned_alloc(sizeof(void *), sizeof(void *));
+	assert(p != NULL && (uintptr_t)p % sizeof(void *) == 0);
+	free(p);
+
+	p = aligned_alloc(256, 256);
+	assert(p != NULL && (uintptr_t)p % 256 == 0);
+	free(p);
+
+	// small alignments are okay
+	p = aligned_alloc(1, 8);
+	assert(p != NULL);
+	free(p);
+	p = aligned_alloc(1, 1);
+	assert(p != NULL);
+	free(p);
+
+	// It seems that glibc doesn't report error in these cases.
+#if !(defined(USE_HOST_LIBC) && defined(__GLIBC__))
+	// size % align must be 0
+	p = aligned_alloc(256, 1);
+	assert(errno == EINVAL);
+	assert(p == NULL);
+
+	// align must be a 'valid alignment supported by the implementation'
+	p = aligned_alloc(3, 1);
+	assert(errno == EINVAL);
+	assert(p == NULL);
+#endif
+
+	return 0;
+}