lib: add libc and micro libc

lib/libc/string/strcmp.c

@@ -0,0 +1,21 @@
+int strcmp(const char *s1, const char *s2)
+{
+	int i;
+	for (i = 0; s1[i] == s2[i]; i++)
+		if (s1[i] == '\0')
+			return 0;
+
+	return s1[i] - s2[i];
+}
+
+int strncmp(const char *s1, const char *s2, unsigned long n)
+{
+	for (; n > 0; s1++, s2++, --n)
+		if (*s1 != *s2)
+			return ((*(unsigned char *)s1 < *(unsigned char *)s2)
+			                ? -1
+			                : 1);
+		else if (*s1 == '\0')
+			return 0;
+	return 0;
+}