doc: Note that rename() is only partially implemented.

Replacing of existing files is not supported. See #2169.

doc/posix1003.1/ch05.t

@@ -108,7 +108,7 @@ rmdir(), Function, Implemented
 @subsection Rename a File
 
 @example
-rename(), Function, Implemented
+rename(), Function, Partial Implementation
 @end example
 
 @section File Characteristics

doc/posix1003.1/ch08.t

@@ -101,6 +101,7 @@ putc(), Function, Implemented
 putchar(), Function, Implemented
 puts(), Function, Implemented
 remove(), Function, Implemented
+rename(), Function, Partial Implementation
 rewind(), Function, Implemented
 scanf(), Function, Implemented
 fscanf(), Function, Implemented

doc/posix1003.1/compliance_list

@@ -255,7 +255,7 @@ readdir(), Supported
 readdir_r(), Supported
 realloc(), Supported
 remove(), Supported
-rename(), Supported
+rename(), see note 2
 rewind(), Supported
 rewinddir(), Supported
 rmdir(), Supported