qt/main: Make title string more i18n-friendly

Currently, whether or not the title is 32-bit or 64-bit was being
appended as a suffix to the title, which is fine for left-to-right
languages, but may not always fly so smoothly with some right-to-left
languages.

We also weren't marking that portion of the string as translatable,
which prevents translators from translating part of the title string.