chm, dvi: Fix build with compiler flags after removing kdelibs4support

After removing kdelibs4support, these flags are enabled:
    -DQT_USE_FAST_OPERATOR_PLUS -DQT_NO_CAST_TO_ASCII
    -DQT_NO_CAST_FROM_ASCII -DQT_NO_URL_CAST_FROM_STRING
    -DQT_NO_CAST_FROM_BYTEARRAY

So wrap naked string and character literals in QStringLiteral,
QLatin1Char and QLatin1String as appropriate.

To more easily see the changes, use «git show --color-words».

Thank $DEITY for vim macros.