Update or add comments to files and functions for use by Doxygen.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12139 6f19259b-4bc3-4df7-8a09-765794883524

StdLib/LibC/Stdio/fgetpos.c

@@ -56,7 +56,7 @@ fgetpos(FILE *fp, fpos_t *pos)
   _DIAGASSERT(fp != NULL);
   _DIAGASSERT(pos != NULL);
 
-  if(fp == NULL) {
+  if((fp == NULL) || (pos == NULL)) {
     errno = EINVAL;
     return (EOF);
   }