texstudio-2.12.10-bp152.3.17

- Use source url
- Drop conditionals for older distros, they fail to build anyways
- Use spec-cleaner to modernise spec file

- Update to version 2.12.10
  * bug fixes
  * fix structure view with Qt >5.10
- Update to version 2.12.8
  * improved tokenizer for syntax checking and completion
  * pressing Ctrl+F while the editor search has focus opens the
    extended search, i.e., you'll get extended search by pressing
    Ctrl+F twice
  * automatically insert math delimiters ($) when inserting a math
    command outside of a math env (can be turned off, default on)
  * change copy behavior of multiple cursors from selection order
    to line order
  * file list is now a transparent popup window: closes when clicked
    outside
  * combine file conflict and show diff dialog
  * fix file watcher not recognizing multiple changes to a file in
    quick succession
  * improved detection of package names when opening texdoc
  * new symbol panel layout
  * some touch scrolling on certain panels
  * updated synctex and poppler libraries for pdf viewer
  * fix undo when a snippet is inserted and a selection is inserted
    as well
  * fix some parts of the editor background may not be drawn in the
    correct color
  * build for OSX High Sierra
  * various other fixes