BUG: MANTIS-1112 (File not found if filename contains accents when using GUI) Replaced QString::toAscii() by QFile::encodeName() when converting filenames to std::string and used QFile::decodeName() when converting std::string filenames to QString ones.

itkStaticConstMacro has some modification in ITK 4.9+
as a result of VLV performance enhancements. This gives
link errors in 3rdParty trunk which use ITK 4.9. Using
enum directly gives more clarity and was an easy fix.

This reverts commit f72c58b7.