Less version 457

Version 457 was released on 8 Dec 2012.

These are the differences between version 451 and version 457:

• Allow backslash escaping of metacharacters in LESS environment variable if the --use-backslash option is set.
• Don't quit if syntax errors are found in command line options.
• Increase sizes of some internal buffers.
• Fix configure bug with --with-regex=none.
• Fix crash with "stty rows 0".
• Fix Win32 attribute display bug.