Log Message:
Update to 7.3.1

Changelog:
2015-09-30: Version 7.3.1

  * New: Simplified Chinese translation of messages and manual.
  * Fix: Compilation error "'wchar_t' undeclared" when Unicode support \ 
is disabled.
  * Fix: Compilation errors when MinGW compiler was used (MinGW-w64 was OK).

2015-08-24: Version 7.3

  * New: Unicode file name support on Windows.
  * Fix: Options -ul and -ub caused option -i to report wrong BOM for no_bom.

2015-07-01: Version 7.2.3

  * Fix: Check for file I/O errors while reading input files, and added
    a few missing checks while writing output files.
  * Fix: Compilation for msys.