Add sys_nerr and sys_errlist.

Also keep the canonical errno list in LibC for now. The kernel gets it
from there. This makes building 3rd party code easier.

..also fix broken strchr().

Kernel/errno.h

@@ -1,40 +1,3 @@
 #pragma once
 
-#define EPERM      1    // Operation not permitted
-#define ENOENT     2    // No such file or directory
-#define ESRCH      3    // No such process
-#define EINTR      4    // Interrupted system call
-#define EIO        5    // I/O error
-#define ENXIO      6    // No such device or address
-#define E2BIG      7    // Argument list too long
-#define ENOEXEC    8    // Exec format error
-#define EBADF      9    // Bad file number
-#define ECHILD    10    // No child processes
-#define EAGAIN    11    // Try again
-#define ENOMEM    12    // Out of memory
-#define EACCES    13    // Permission denied
-#define EFAULT    14    // Bad address
-#define ENOTBLK   15    // Block device required
-#define EBUSY     16    // Device or resource busy
-#define EEXIST    17    // File exists
-#define EXDEV     18    // Cross-device link
-#define ENODEV    19    // No such device
-#define ENOTDIR   20    // Not a directory
-#define EISDIR    21    // Is a directory
-#define EINVAL    22    // Invalid argument
-#define ENFILE    23    // File table overflow
-#define EMFILE    24    // Too many open files
-#define ENOTTY    25    // Not a typewriter
-#define ETXTBSY   26    // Text file busy
-#define EFBIG     27    // File too large
-#define ENOSPC    28    // No space left on device
-#define ESPIPE    29    // Illegal seek
-#define EROFS     30    // Read-only file system
-#define EMLINK    31    // Too many links
-#define EPIPE     32    // Broken pipe
-#define EDOM      33    // Math argument out of domain of func
-#define ERANGE    34    // Math result not representable
-#define ENAMETOOLONG 36 // Name too long
-#define ELOOP     40    // Too many symbolic links
-#define EOVERFLOW 75    // Value too large for defined data type
-#define ENOTIMPL 999    // Not implemented
+#include <LibC/errno_numbers.h>