[Kernel] header files

1. Remove components.h file;
2. Add libc_* files for standard libc definitions;
3. Add rtdbg.h file for simple debug log;
4. Add single list implementation;
5. Change the 'rt_uint8_t' type of cmd to 'int'.

include/libc/libc_fcntl.h

@@ -0,0 +1,57 @@
+/*
+ * fcntl.h file in libc
+ */ 
+#ifndef LIBC_FCNTL_H__
+#define LIBC_FCNTL_H__
+
+#define O_RDONLY         00
+#define O_WRONLY         01
+#define O_RDWR           02
+
+#define O_CREAT        0100
+#define O_EXCL         0200
+#define O_NOCTTY       0400
+#define O_TRUNC       01000
+#define O_APPEND      02000
+#define O_NONBLOCK    04000
+#define O_DSYNC      010000
+#define O_SYNC     04010000
+#define O_RSYNC    04010000
+#define O_DIRECTORY 0200000
+#define O_NOFOLLOW  0400000
+#define O_CLOEXEC  02000000
+
+#define O_ASYNC      020000
+#define O_DIRECT     040000
+#define O_LARGEFILE 0100000
+#define O_NOATIME  01000000
+#define O_PATH    010000000
+#define O_TMPFILE 020200000
+#define O_NDELAY O_NONBLOCK
+
+#define O_SEARCH  O_PATH
+#define O_EXEC    O_PATH
+
+#define O_ACCMODE (03|O_SEARCH)
+
+#define F_DUPFD  0
+#define F_GETFD  1
+#define F_SETFD  2
+#define F_GETFL  3
+#define F_SETFL  4
+
+#define F_SETOWN 8
+#define F_GETOWN 9
+#define F_SETSIG 10
+#define F_GETSIG 11
+
+#define F_GETLK 12
+#define F_SETLK 13
+#define F_SETLKW 14
+
+#define F_SETOWN_EX 15
+#define F_GETOWN_EX 16
+
+#define F_GETOWNER_UIDS 17
+
+#endif