Fix Qt 5 build issues (don't use QString::toAscii)

Change QString::toAscii usages to QString::toLatin1.

Change-Id: I20b08cc7215d79a0e922df99142e7c0d36493a6b
Merge topic 'lookup_table_cleanup' into next

53ca7907 Fix Qt 5 build issues (don't use QString::toAscii)