Fixes to strchr, mkfats, and NxWidgets from Petteri Aimonen

ChangeLog

@@ -4581,3 +4581,8 @@
 	  variables with auto-generated documentation.  The initial checkin
 	  is an incomplete, poorly structured prototype that I hope to
 	  evolve into a useful tool (2014-4-20).
+	* libc/string/lib_strchr.c:  strchr(str, '\0') should return a
+	  pointer to the end of the string, not NULL.  From Petteri
+	  Aimonen (2014-4-22).
+	* fs/fat/fs_writefat.c: mkfatfs was writing the boot code to the
+	  wrong location.  From Petteri Aimonen (2014-4-22).

fs/fat/fs_writefat.c

@@ -212,7 +212,7 @@ static inline void mkfatfs_initmbr(FAR struct fat_format_s *fmt,
 
       /* Boot code may be placed in the remainder of the sector */
 
-      memcpy(&var->fv_sect[BS16_BOOTCODE], var->fv_bootcode, var->fv_bootcodesize);
+      memcpy(&var->fv_sect[BS32_BOOTCODE], var->fv_bootcode, var->fv_bootcodesize);
     }
 
   /* The magic bytes at the end of the MBR are common to FAT12/16/32 */

libc/string/lib_strchr.c

@@ -64,12 +64,17 @@ FAR char *strchr(FAR const char *s, int c)
 {
   if (s)
     {
-      for (; *s; s++)
+      for (; ; s++)
         {
           if (*s == c)
             {
               return (FAR char *)s;
             }
+
+          if (!*s)
+            {
+              break;
+            }
         }
     }