updated Scintilla to v5.3.4, Scinterm to v4.1 and Lexilla to v5.2.4

* actually everything is updated to their current HEADs but the aforementioned versions are close.
* Scintilla uses threads now, so we added checks for pthread.
  To be on the safe side, we imported AX_PTHREAD from the Autoconf archives.
  The flags are kept out of the ordinary build system, though and used only for compiling Scintilla
  and for linking.
  SciTECO may also use threads, but via Glib.
* Scinterm removed SCI_COLOR_PAIR(), so we re-added it to src/interface-curses/interface.c.
* There is an Asciidoc lexer now.
* The <Ix$> interruption bug (see TODO) is not fixed by this upgrade.
  Perhaps the Mac OS version runs better now. Feedback is needed (refs #12).

1 files changed, 0 insertions, 0 deletions

diff --git a/contrib/scintilla b/contrib/scintilla
-Subproject fab670c471c7eea28d43ebaeed14b3c886e2c6e
+Subproject 85ea187540b421d3d99c91019ed484c70d9d1d1