Update editors/texmaker to version 5.1.2

pkgsrc changes:
qt5script is not used anymore, this means that
only qt5declarative is needed as a dependency.
USE_LIBTOOL line removed since qt5 doesn't
use libtool.

Changes from ChangeLog:

version 5.1.1 -> 5.1.2 :
- a bug related to replace action with a regular expression has been fixed
- a bug related to mouse wheel events in the pdf viewer has been fixed
- support for non integer dpi scale factor has been added
  (such as Windows using 125% or 150% scale on laptops)
version 5.1.0 -> 5.1.1 :
- a critical bug on the windows version compiled with msvc 2019 while
  inserting a symbol has been fixed
- a trouble in the syntax highlighting with the verb latex command
  has been fixed
version 5.0.4 -> 5.1.0 :
- compatibility with Qt6 has been added. Texmaker can now be compiled
  with Qt5 (>=5.7) and Qt6 (>= 6.2). This ensures that Texmaker will
  be available for, at least, the next ten years.
- the internal pdf engine (from chromium) has been updated
- hunspell has been updated to 1.7.O
- synctex has been updated to 1.21
- default windows paths are now searched in the windows registry and path
- a potential trouble with user commands beginning with a space has been
  fixed
- the texmaker.appdata.xml file has been updated
- GTK-based theming for systems without a "GTK+" theme has been added
- a bug with the use of latexmk with the use of the "output directory"
  option has been fixed
- the pdf viewer is replaced in the default position on the main screen
  if it has been closed on a screen which is no more connected
- the scale in the pdf viewer is now automatically adapted after
  closing/restoring the list of pages panel
- layout has been improved in the find/replace widgets
- the obsolete use of QTScript has been replaced by QJSEngine
- the ability to change the interface font has been expanded to windows
  and macos
- the ability to check spelling/grammar the text extracted from a pdf
  page in the internal pdf viewer is back (via online languagetool)
- a link to import more spell dictionaries has been added to
  the configuration dialog

(nros)