Fix - .JSON import of chars > 127 on QT5 problem (leading to ??? in texts)

... on QT5 the conversion of chars > 127 did not work (ending with ???)
when loading a .JSON ride file
... by this change the implicite type cast (char to QString) when
calling "unprotect" does not take place any more, so the lexer string
must be 'Local8Bit' to what is has been converted when reading the file
... again QT has changed behavior of locale related processing in QT5
(all this worked fine in QT4)
Merge pull request #1012 from Joern-R/pull4

Fix - .JSON import of chars > 127 on QT5 problem (leading to ? in text fields)