QRencode: Add fallback for Linux distros that don't provide unversion…

[selmf]

…ed library symlinks

With the current configuration, YACReaderLibrary on Linux searches for "libqrencode.so" and will fail to load it if only "libqrencode.so.x" is installed. To fix this, this PR adds a check to see if the library was loaded successfully and requests an exact version of the library if the load failed. By providing the version, QLibrary is made aware that it should look for "libqrencode.so.4" and the load works.